multires.c

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/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software  Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2007 by Nicholas Bishop
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): none yet.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include "MEM_guardedalloc.h"

/* for reading old multires */
#define DNA_DEPRECATED_ALLOW

#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"
#include "DNA_object_types.h"
#include "DNA_scene_types.h"

#include "BLI_blenlib.h"
#include "BLI_math.h"
#include "BLI_pbvh.h"
#include "BLI_editVert.h"
#include "BLI_utildefines.h"

#include "BKE_cdderivedmesh.h"
#include "BKE_mesh.h"
#include "BKE_modifier.h"
#include "BKE_multires.h"
#include "BKE_paint.h"
#include "BKE_scene.h"
#include "BKE_subsurf.h"

#include "BKE_object.h"

#include "CCGSubSurf.h"

#include <math.h>
#include <string.h>

/* MULTIRES MODIFIER */
static const int multires_max_levels = 13;
static const int multires_grid_tot[] = {0, 4, 9, 25, 81, 289, 1089, 4225, 16641, 66049, 263169, 1050625, 4198401, 16785409};
static const int multires_side_tot[] = {0, 2, 3, 5,  9,  17,  33,   65,   129,   257,   513,    1025,    2049,    4097};

static void multires_mvert_to_ss(DerivedMesh *dm, MVert *mvert);
static void multiresModifier_disp_run(DerivedMesh *dm, Mesh *me, int invert, int add, DMGridData **oldGridData, int totlvl);

DerivedMesh *get_multires_dm(Scene *scene, MultiresModifierData *mmd, Object *ob)
{
    ModifierData *md= (ModifierData *)mmd;
    ModifierTypeInfo *mti = modifierType_getInfo(md->type);
    DerivedMesh *tdm = mesh_get_derived_deform(scene, ob, CD_MASK_BAREMESH);
    DerivedMesh *dm;

    dm = mti->applyModifier(md, ob, tdm, 0, 1);
    if (dm == tdm) {
        dm = CDDM_copy(tdm);
    }

    return dm;
}

MultiresModifierData *find_multires_modifier_before(Scene *scene, ModifierData *lastmd)
{
    ModifierData *md;

    for(md = lastmd; md; md = md->prev) {
        if(md->type == eModifierType_Multires) {
            if (modifier_isEnabled(scene, md, eModifierMode_Realtime))
                return (MultiresModifierData*)md;
        }
    }

    return NULL;
}

/* used for applying scale on mdisps layer and syncing subdivide levels when joining objects
   use_first - return first multires modifier if all multires'es are disabled
*/
MultiresModifierData *get_multires_modifier(Scene *scene, Object *ob, int use_first)
{
    ModifierData *md;
    MultiresModifierData *mmd= NULL, *firstmmd= NULL;

    /* find first active multires modifier */
    for(md = ob->modifiers.first; md; md = md->next) {
        if(md->type == eModifierType_Multires) {
            if(!firstmmd)
                firstmmd= (MultiresModifierData*)md;

            if (modifier_isEnabled(scene, md, eModifierMode_Realtime)) {
                mmd= (MultiresModifierData*)md;
                break;
            }
        }
    }

    if(!mmd && use_first) {
        /* active multires have not been found
           try to use first one */
        return firstmmd;
    }

    return mmd;
}

static int multires_get_level(Object *ob, MultiresModifierData *mmd, int render)
{
    if(render)
        return (mmd->modifier.scene)? get_render_subsurf_level(&mmd->modifier.scene->r, mmd->renderlvl): mmd->renderlvl;
    else if(ob->mode == OB_MODE_SCULPT)
        return mmd->sculptlvl;
    else
        return (mmd->modifier.scene)? get_render_subsurf_level(&mmd->modifier.scene->r, mmd->lvl): mmd->lvl;
}

static void multires_set_tot_level(Object *ob, MultiresModifierData *mmd, int lvl)
{
    mmd->totlvl = lvl;

    if(ob->mode != OB_MODE_SCULPT)
        mmd->lvl = CLAMPIS(MAX2(mmd->lvl, lvl), 0, mmd->totlvl);

    mmd->sculptlvl = CLAMPIS(MAX2(mmd->sculptlvl, lvl), 0, mmd->totlvl);
    mmd->renderlvl = CLAMPIS(MAX2(mmd->renderlvl, lvl), 0, mmd->totlvl);
}

static void multires_dm_mark_as_modified(DerivedMesh *dm)
{
    CCGDerivedMesh *ccgdm = (CCGDerivedMesh*)dm;
    ccgdm->multires.modified = 1;
}

void multires_mark_as_modified(Object *ob)
{
    if(ob && ob->derivedFinal)
        multires_dm_mark_as_modified(ob->derivedFinal);
}

void multires_force_update(Object *ob)
{
    if(ob) {
        if(ob->derivedFinal) {
            ob->derivedFinal->needsFree =1;
            ob->derivedFinal->release(ob->derivedFinal);
            ob->derivedFinal = NULL;
        }
        if(ob->sculpt && ob->sculpt->pbvh) {
            BLI_pbvh_free(ob->sculpt->pbvh);
            ob->sculpt->pbvh= NULL;
        }
    }
}

void multires_force_external_reload(Object *ob)
{
    Mesh *me = get_mesh(ob);

    CustomData_external_reload(&me->fdata, &me->id, CD_MASK_MDISPS, me->totface);
    multires_force_update(ob);
}

void multires_force_render_update(Object *ob)
{
    if(ob && (ob->mode & OB_MODE_SCULPT) && modifiers_findByType(ob, eModifierType_Multires))
        multires_force_update(ob);
}

int multiresModifier_reshapeFromDM(Scene *scene, MultiresModifierData *mmd,
                Object *ob, DerivedMesh *srcdm)
{
    DerivedMesh *mrdm = get_multires_dm (scene, mmd, ob);

    if(mrdm && srcdm && mrdm->getNumVerts(mrdm) == srcdm->getNumVerts(srcdm)) {
        multires_mvert_to_ss(mrdm, srcdm->getVertArray(srcdm));

        multires_dm_mark_as_modified(mrdm);
        multires_force_update(ob);

        mrdm->release(mrdm);

        return 1;
    }

    if(mrdm) mrdm->release(mrdm);

    return 0;
}

/* Returns 1 on success, 0 if the src's totvert doesn't match */
int multiresModifier_reshape(Scene *scene, MultiresModifierData *mmd, Object *dst, Object *src)
{
    DerivedMesh *srcdm = mesh_get_derived_final(scene, src, CD_MASK_BAREMESH);
    return multiresModifier_reshapeFromDM(scene, mmd, dst, srcdm);
}

int multiresModifier_reshapeFromDeformMod(Scene *scene, MultiresModifierData *mmd,
                Object *ob, ModifierData *md)
{
    ModifierTypeInfo *mti = modifierType_getInfo(md->type);
    DerivedMesh *dm, *ndm;
    int numVerts, result;
    float (*deformedVerts)[3];

    if(multires_get_level(ob, mmd, 0) == 0)
        return 0;

    /* Create DerivedMesh for deformation modifier */
    dm = get_multires_dm(scene, mmd, ob);
    numVerts= dm->getNumVerts(dm);
    deformedVerts= MEM_callocN(sizeof(float)*numVerts*3, "multiresReshape_deformVerts");

    dm->getVertCos(dm, deformedVerts);
    mti->deformVerts(md, ob, dm, deformedVerts, numVerts, 0, 0);

    ndm= CDDM_copy(dm);
    CDDM_apply_vert_coords(ndm, deformedVerts);

    MEM_freeN(deformedVerts);
    dm->release(dm);

    /* Reshaping */
    result= multiresModifier_reshapeFromDM(scene, mmd, ob, ndm);

    /* Cleanup */
    ndm->release(ndm);

    return result;
}

/* reset the multires levels to match the number of mdisps */
static int get_levels_from_disps(Object *ob)
{
    Mesh *me = ob->data;
    MDisps *mdisp;
    int i, totlvl= 0;

    mdisp = CustomData_get_layer(&me->fdata, CD_MDISPS);

    for(i = 0; i < me->totface; ++i, ++mdisp) {
        int S = me->mface[i].v4 ? 4 : 3;

        if(mdisp->totdisp == 0) continue;

        while(1) {
            int side = (1 << (totlvl-1)) + 1;
            int lvl_totdisp = side*side*S;
            if(mdisp->totdisp == lvl_totdisp)
                break;
            else if(mdisp->totdisp < lvl_totdisp)
                --totlvl;
            else
                ++totlvl;

        }
    }

    return totlvl;
}

/* reset the multires levels to match the number of mdisps */
void multiresModifier_set_levels_from_disps(MultiresModifierData *mmd, Object *ob)
{
    Mesh *me = ob->data;
    MDisps *mdisp;

    if(me->edit_mesh)
        mdisp = CustomData_get_layer(&me->edit_mesh->fdata, CD_MDISPS);
    else
        mdisp = CustomData_get_layer(&me->fdata, CD_MDISPS);

    if(mdisp) {
        mmd->totlvl = get_levels_from_disps(ob);
        mmd->lvl = MIN2(mmd->sculptlvl, mmd->totlvl);
        mmd->sculptlvl = MIN2(mmd->sculptlvl, mmd->totlvl);
        mmd->renderlvl = MIN2(mmd->renderlvl, mmd->totlvl);
    }
}

static void multires_set_tot_mdisps(Mesh *me, int lvl)
{
    MDisps *mdisps= CustomData_get_layer(&me->fdata, CD_MDISPS);
    int i;

    if(mdisps) {
        for(i = 0; i < me->totface; i++) {
            if(mdisps[i].totdisp == 0) {
                int nvert = (me->mface[i].v4)? 4: 3;
                mdisps[i].totdisp = multires_grid_tot[lvl]*nvert;
            }
        }
    }
}

static void multires_reallocate_mdisps(Mesh *me, MDisps *mdisps, int lvl)
{
    int i;

    /* reallocate displacements to be filled in */
    for(i = 0; i < me->totface; ++i) {
        int nvert = (me->mface[i].v4)? 4: 3;
        int totdisp = multires_grid_tot[lvl]*nvert;
        float (*disps)[3] = MEM_callocN(sizeof(float) * 3 * totdisp, "multires disps");

        if(mdisps[i].disps)
            MEM_freeN(mdisps[i].disps);

        mdisps[i].disps = disps;
        mdisps[i].totdisp = totdisp;
    }
}

static void column_vectors_to_mat3(float mat[][3], float v1[3], float v2[3], float v3[3])
{
    copy_v3_v3(mat[0], v1);
    copy_v3_v3(mat[1], v2);
    copy_v3_v3(mat[2], v3);
}

static void multires_copy_grid(float (*gridA)[3], float (*gridB)[3], int sizeA, int sizeB)
{
    int x, y, j, skip;

    if(sizeA > sizeB) {
        skip = (sizeA-1)/(sizeB-1);

        for(j = 0, y = 0; y < sizeB; y++)
            for(x = 0; x < sizeB; x++, j++)
                copy_v3_v3(gridA[y*skip*sizeA + x*skip], gridB[j]);
    }
    else {
        skip = (sizeB-1)/(sizeA-1);

        for(j = 0, y = 0; y < sizeA; y++)
            for(x = 0; x < sizeA; x++, j++)
                copy_v3_v3(gridA[j], gridB[y*skip*sizeB + x*skip]);
    }
}

static void multires_copy_dm_grid(DMGridData *gridA, DMGridData *gridB, int sizeA, int sizeB)
{
    int x, y, j, skip;

    if(sizeA > sizeB) {
        skip = (sizeA-1)/(sizeB-1);

        for(j = 0, y = 0; y < sizeB; y++)
            for(x = 0; x < sizeB; x++, j++)
                copy_v3_v3(gridA[y*skip*sizeA + x*skip].co, gridB[j].co);
    }
    else {
        skip = (sizeB-1)/(sizeA-1);

        for(j = 0, y = 0; y < sizeA; y++)
            for(x = 0; x < sizeA; x++, j++)
                copy_v3_v3(gridA[j].co, gridB[y*skip*sizeB + x*skip].co);
    }
}

static void multires_del_higher(MultiresModifierData *mmd, Object *ob, int lvl)
{
    Mesh *me = (Mesh*)ob->data;
    int levels = mmd->totlvl - lvl;
    MDisps *mdisps;

    multires_set_tot_mdisps(me, mmd->totlvl);
    CustomData_external_read(&me->fdata, &me->id, CD_MASK_MDISPS, me->totface);
    mdisps= CustomData_get_layer(&me->fdata, CD_MDISPS);

    multires_force_update(ob);

    if(mdisps && levels > 0) {
        if(lvl > 0) {
            int nsize = multires_side_tot[lvl];
            int hsize = multires_side_tot[mmd->totlvl];
            int i;

            for(i = 0; i < me->totface; ++i) {
                MDisps *mdisp= &mdisps[i];
                float (*disps)[3], (*ndisps)[3], (*hdisps)[3];
                int nvert = (me->mface[i].v4)? 4: 3;
                int totdisp = multires_grid_tot[lvl]*nvert;
                int S;

                disps = MEM_callocN(sizeof(float) * 3 * totdisp, "multires disps");

                ndisps = disps;
                hdisps = mdisp->disps;

                for(S = 0; S < nvert; S++) {
                    multires_copy_grid(ndisps, hdisps, nsize, hsize);

                    ndisps += nsize*nsize;
                    hdisps += hsize*hsize;
                }

                MEM_freeN(mdisp->disps);
                mdisp->disps = disps;
                mdisp->totdisp = totdisp;
            }
        }
        else {
            CustomData_external_remove(&me->fdata, &me->id, CD_MDISPS, me->totface);
            CustomData_free_layer_active(&me->fdata, CD_MDISPS, me->totface);
        }
    }

    multires_set_tot_level(ob, mmd, lvl);
}

/* direction=1 for delete higher, direction=0 for lower (not implemented yet) */
void multiresModifier_del_levels(MultiresModifierData *mmd, Object *ob, int direction)
{
    Mesh *me = get_mesh(ob);
    int lvl = multires_get_level(ob, mmd, 0);
    int levels = mmd->totlvl - lvl;
    MDisps *mdisps;

    multires_set_tot_mdisps(me, mmd->totlvl);
    CustomData_external_read(&me->fdata, &me->id, CD_MASK_MDISPS, me->totface);
    mdisps= CustomData_get_layer(&me->fdata, CD_MDISPS);

    multires_force_update(ob);

    if(mdisps && levels > 0 && direction == 1) {
        multires_del_higher(mmd, ob, lvl);
    }

    multires_set_tot_level(ob, mmd, lvl);
}

static DerivedMesh *multires_dm_create_local(Object *ob, DerivedMesh *dm, int lvl, int totlvl, int simple)
{
    MultiresModifierData mmd= {{NULL}};

    mmd.lvl = lvl;
    mmd.sculptlvl = lvl;
    mmd.renderlvl = lvl;
    mmd.totlvl = totlvl;
    mmd.simple = simple;

    return multires_dm_create_from_derived(&mmd, 1, dm, ob, 0, 0);
}

static DerivedMesh *subsurf_dm_create_local(Object *ob, DerivedMesh *dm, int lvl, int simple, int optimal, int plain_uv)
{
    SubsurfModifierData smd= {{NULL}};

    smd.levels = smd.renderLevels = lvl;
    if(!plain_uv)
        smd.flags |= eSubsurfModifierFlag_SubsurfUv;
    if(simple)
        smd.subdivType = ME_SIMPLE_SUBSURF;
    if(optimal)
        smd.flags |= eSubsurfModifierFlag_ControlEdges;

    return subsurf_make_derived_from_derived(dm, &smd, 0, NULL, 0, 0, (ob->mode & OB_MODE_EDIT));
}



/* assumes no is normalized; return value's sign is negative if v is on
   the other side of the plane */
static float v3_dist_from_plane(float v[3], float center[3], float no[3])
{
    float s[3];
    sub_v3_v3v3(s, v, center);
    return dot_v3v3(s, no);
}

void multiresModifier_base_apply(MultiresModifierData *mmd, Object *ob)
{
    DerivedMesh *cddm, *dispdm, *origdm;
    Mesh *me;
    ListBase *fmap;
    float (*origco)[3];
    int i, j, offset, totlvl;

    multires_force_update(ob);

    me = get_mesh(ob);
    totlvl = mmd->totlvl;

    /* nothing to do */
    if(!totlvl)
        return;

    /* XXX - probably not necessary to regenerate the cddm so much? */

    /* generate highest level with displacements */
    cddm = CDDM_from_mesh(me, NULL);
    DM_set_only_copy(cddm, CD_MASK_BAREMESH);
    dispdm = multires_dm_create_local(ob, cddm, totlvl, totlvl, 0);
    cddm->release(cddm);

    /* copy the new locations of the base verts into the mesh */
    offset = dispdm->getNumVerts(dispdm) - me->totvert;
    for(i = 0; i < me->totvert; ++i) {
        dispdm->getVertCo(dispdm, offset + i, me->mvert[i].co);
    }

    /* heuristic to produce a better-fitting base mesh */

    cddm = CDDM_from_mesh(me, NULL);
    fmap = cddm->getFaceMap(ob, cddm);
    origco = MEM_callocN(sizeof(float)*3*me->totvert, "multires apply base origco");
    for(i = 0; i < me->totvert ;++i)
        copy_v3_v3(origco[i], me->mvert[i].co);

    for(i = 0; i < me->totvert; ++i) {
        IndexNode *n;
        float avg_no[3] = {0,0,0}, center[3] = {0,0,0}, push[3];
        float dist;
        int tot;

        /* don't adjust verts not used by at least one face */
        if(!fmap[i].first)
            continue;

        /* find center */
        for(n = fmap[i].first, tot = 0; n; n = n->next) {
            MFace *f = &me->mface[n->index];
            int S = f->v4 ? 4 : 3;
            
            /* this double counts, not sure if that's bad or good */
            for(j = 0; j < S; ++j) {
                int vndx = (&f->v1)[j];
                if(vndx != i) {
                    add_v3_v3(center, origco[vndx]);
                    ++tot;
                }
            }
        }
        mul_v3_fl(center, 1.0f / tot);

        /* find normal */
        for(n = fmap[i].first; n; n = n->next) {
            MFace *f = &me->mface[n->index];
            int S = f->v4 ? 4 : 3;
            float v[4][3], no[3];
            
            for(j = 0; j < S; ++j) {
                int vndx = (&f->v1)[j];
                if(vndx == i)
                    copy_v3_v3(v[j], center);
                else
                    copy_v3_v3(v[j], origco[vndx]);
            }
            
            if(S == 4)
                normal_quad_v3(no, v[0], v[1], v[2], v[3]);
            else
                normal_tri_v3(no, v[0], v[1], v[2]);
            add_v3_v3(avg_no, no);
        }
        normalize_v3(avg_no);

        /* push vertex away from the plane */
        dist = v3_dist_from_plane(me->mvert[i].co, center, avg_no);
        copy_v3_v3(push, avg_no);
        mul_v3_fl(push, dist);
        add_v3_v3(me->mvert[i].co, push);
        
    }

    MEM_freeN(origco);
    cddm->release(cddm);

    /* subdivide the mesh to highest level without displacements */
    cddm = CDDM_from_mesh(me, NULL);
    DM_set_only_copy(cddm, CD_MASK_BAREMESH);
    origdm = subsurf_dm_create_local(ob, cddm, totlvl, 0, 0, mmd->flags & eMultiresModifierFlag_PlainUv);
    cddm->release(cddm);

    /* calc disps */
    multiresModifier_disp_run(dispdm, me, 1, 0, origdm->getGridData(origdm), totlvl);

    origdm->release(origdm);
    dispdm->release(dispdm);
}

static void multires_subdivide(MultiresModifierData *mmd, Object *ob, int totlvl, int updateblock, int simple)
{
    Mesh *me = ob->data;
    MDisps *mdisps;
    int lvl= mmd->totlvl;

    if(totlvl > multires_max_levels)
        return;

    multires_force_update(ob);

    mdisps = CustomData_get_layer(&me->fdata, CD_MDISPS);
    if(!mdisps)
        mdisps = CustomData_add_layer(&me->fdata, CD_MDISPS, CD_DEFAULT, NULL, me->totface);

    if(mdisps->disps && !updateblock && totlvl > 1) {
        /* upsample */
        DerivedMesh *lowdm, *cddm, *highdm;
        DMGridData **highGridData, **lowGridData, **subGridData;
        CCGSubSurf *ss;
        int i, numGrids, highGridSize, lowGridSize;

        /* create subsurf DM from original mesh at high level */
        cddm = CDDM_from_mesh(me, NULL);
        DM_set_only_copy(cddm, CD_MASK_BAREMESH);
        highdm = subsurf_dm_create_local(ob, cddm, totlvl, simple, 0, mmd->flags & eMultiresModifierFlag_PlainUv);

        /* create multires DM from original mesh at low level */
        lowdm = multires_dm_create_local(ob, cddm, lvl, lvl, simple);
        cddm->release(cddm);

        /* copy subsurf grids and replace them with low displaced grids */
        numGrids = highdm->getNumGrids(highdm);
        highGridSize = highdm->getGridSize(highdm);
        highGridData = highdm->getGridData(highdm);
        lowGridSize = lowdm->getGridSize(lowdm);
        lowGridData = lowdm->getGridData(lowdm);

        subGridData = MEM_callocN(sizeof(float*)*numGrids, "subGridData*");

        for(i = 0; i < numGrids; ++i) {
            /* backup subsurf grids */
            subGridData[i] = MEM_callocN(sizeof(DMGridData)*highGridSize*highGridSize, "subGridData");
            memcpy(subGridData[i], highGridData[i], sizeof(DMGridData)*highGridSize*highGridSize);

            /* overwrite with current displaced grids */
            multires_copy_dm_grid(highGridData[i], lowGridData[i], highGridSize, lowGridSize);
        }

        /* low lower level dm no longer needed at this point */
        lowdm->release(lowdm);

        /* subsurf higher levels again with displaced data */
        ss= ((CCGDerivedMesh*)highdm)->ss;
        ccgSubSurf_updateFromFaces(ss, lvl, NULL, 0);
        ccgSubSurf_updateLevels(ss, lvl, NULL, 0);

        /* reallocate displacements */
        multires_reallocate_mdisps(me, mdisps, totlvl); 

        /* compute displacements */
        multiresModifier_disp_run(highdm, me, 1, 0, subGridData, totlvl);

        /* free */
        highdm->release(highdm);
        for(i = 0; i < numGrids; ++i)
            MEM_freeN(subGridData[i]);
        MEM_freeN(subGridData);
    }
    else {
        /* only reallocate, nothing to upsample */
        multires_reallocate_mdisps(me, mdisps, totlvl); 
    }

    multires_set_tot_level(ob, mmd, totlvl);
}

void multiresModifier_subdivide(MultiresModifierData *mmd, Object *ob, int updateblock, int simple)
{
    multires_subdivide(mmd, ob, mmd->totlvl+1, updateblock, simple);
}

static void grid_tangent(int gridSize, int index, int x, int y, int axis, DMGridData **gridData, float t[3])
{
    if(axis == 0) {
        if(x == gridSize - 1) {
            if(y == gridSize - 1)
                sub_v3_v3v3(t, gridData[index][x + gridSize*(y - 1)].co, gridData[index][x - 1 + gridSize*(y - 1)].co);
            else
                sub_v3_v3v3(t, gridData[index][x + gridSize*y].co, gridData[index][x - 1 + gridSize*y].co);
        }
        else
            sub_v3_v3v3(t, gridData[index][x + 1 + gridSize*y].co, gridData[index][x + gridSize*y].co);
    }
    else if(axis == 1) {
        if(y == gridSize - 1) {
            if(x == gridSize - 1)
                sub_v3_v3v3(t, gridData[index][x - 1 + gridSize*y].co, gridData[index][x - 1 + gridSize*(y - 1)].co);
            else
                sub_v3_v3v3(t, gridData[index][x + gridSize*y].co, gridData[index][x + gridSize*(y - 1)].co);
        }
        else
            sub_v3_v3v3(t, gridData[index][x + gridSize*(y + 1)].co, gridData[index][x + gridSize*y].co);
    }
}

static void multiresModifier_disp_run(DerivedMesh *dm, Mesh *me, int invert, int add, DMGridData **oldGridData, int totlvl)
{
    CCGDerivedMesh *ccgdm = (CCGDerivedMesh*)dm;
    DMGridData **gridData, **subGridData;
    MFace *mface = me->mface;
    MDisps *mdisps = CustomData_get_layer(&me->fdata, CD_MDISPS);
    int *gridOffset;
    int i, /*numGrids,*/ gridSize, dGridSize, dSkip;

    if(!mdisps) {
        if(invert)
            mdisps = CustomData_add_layer(&me->fdata, CD_MDISPS, CD_DEFAULT, NULL, me->totface);
        else
            return;
    }

    /*numGrids = dm->getNumGrids(dm);*/ /*UNUSED*/
    gridSize = dm->getGridSize(dm);
    gridData = dm->getGridData(dm);
    gridOffset = dm->getGridOffset(dm);
    subGridData = (oldGridData)? oldGridData: gridData;

    dGridSize = multires_side_tot[totlvl];
    dSkip = (dGridSize-1)/(gridSize-1);

    #pragma omp parallel for private(i) if(me->totface*gridSize*gridSize*4 >= CCG_OMP_LIMIT)
    for(i = 0; i < me->totface; ++i) {
        const int numVerts = mface[i].v4 ? 4 : 3;
        MDisps *mdisp = &mdisps[i];
        int S, x, y, gIndex = gridOffset[i];

        /* when adding new faces in edit mode, need to allocate disps */
        if(!mdisp->disps)
        #pragma omp critical
        {
            multires_reallocate_mdisps(me, mdisps, totlvl);
        }

        for(S = 0; S < numVerts; ++S, ++gIndex) {
            DMGridData *grid = gridData[gIndex];
            DMGridData *subgrid = subGridData[gIndex];
            float (*dispgrid)[3] = &mdisp->disps[S*dGridSize*dGridSize];

            for(y = 0; y < gridSize; y++) {
                for(x = 0; x < gridSize; x++) {
                    float *co = grid[x + y*gridSize].co;
                    float *sco = subgrid[x + y*gridSize].co;
                    float *no = subgrid[x + y*gridSize].no;
                    float *data = dispgrid[dGridSize*y*dSkip + x*dSkip];
                    float mat[3][3], tx[3], ty[3], disp[3], d[3];

                    /* construct tangent space matrix */
                    grid_tangent(gridSize, gIndex, x, y, 0, subGridData, tx);
                    normalize_v3(tx);

                    grid_tangent(gridSize, gIndex, x, y, 1, subGridData, ty);
                    normalize_v3(ty);

                    //mul_v3_fl(tx, 1.0f/(gridSize-1));
                    //mul_v3_fl(ty, 1.0f/(gridSize-1));
                    //cross_v3_v3v3(no, tx, ty);

                    column_vectors_to_mat3(mat, tx, ty, no);

                    if(!invert) {
                        /* convert to object space and add */
                        mul_v3_m3v3(disp, mat, data);
                        add_v3_v3v3(co, sco, disp);
                    }
                    else if(!add) {
                        /* convert difference to tangent space */
                        sub_v3_v3v3(disp, co, sco);
                        invert_m3(mat);
                        mul_v3_m3v3(data, mat, disp);
                    }
                    else {
                        /* convert difference to tangent space */
                        invert_m3(mat);
                        mul_v3_m3v3(d, mat, co);
                        add_v3_v3(data, d);
                    }
                }
            }
        }
    }

    if(!invert) {
        ccgSubSurf_stitchFaces(ccgdm->ss, 0, NULL, 0);
        ccgSubSurf_updateNormals(ccgdm->ss, NULL, 0);
    }
}

static void multiresModifier_update(DerivedMesh *dm)
{
    CCGDerivedMesh *ccgdm= (CCGDerivedMesh*)dm;
    Object *ob;
    Mesh *me;
    MDisps *mdisps;
    MultiresModifierData *mmd;

    ob = ccgdm->multires.ob;
    me = ccgdm->multires.ob->data;
    mmd = ccgdm->multires.mmd;
    multires_set_tot_mdisps(me, mmd->totlvl);
    CustomData_external_read(&me->fdata, &me->id, CD_MASK_MDISPS, me->totface);
    mdisps = CustomData_get_layer(&me->fdata, CD_MDISPS);

    if(mdisps) {
        int lvl = ccgdm->multires.lvl;
        int totlvl = ccgdm->multires.totlvl;
        
        if(lvl < totlvl) {
            Mesh *me = ob->data;
            DerivedMesh *lowdm, *cddm, *highdm;
            DMGridData **highGridData, **lowGridData, **subGridData, **gridData, *diffGrid;
            CCGSubSurf *ss;
            int i, j, numGrids, highGridSize, lowGridSize;

            /* create subsurf DM from original mesh at high level */
            if (ob->derivedDeform) cddm = CDDM_copy(ob->derivedDeform);
            else cddm = CDDM_from_mesh(me, NULL);
            DM_set_only_copy(cddm, CD_MASK_BAREMESH);

            highdm = subsurf_dm_create_local(ob, cddm, totlvl, mmd->simple, 0, mmd->flags & eMultiresModifierFlag_PlainUv);

            /* create multires DM from original mesh and displacements */
            lowdm = multires_dm_create_local(ob, cddm, lvl, totlvl, mmd->simple);
            cddm->release(cddm);

            /* gather grid data */
            numGrids = highdm->getNumGrids(highdm);
            highGridSize = highdm->getGridSize(highdm);
            highGridData = highdm->getGridData(highdm);
            lowGridSize = lowdm->getGridSize(lowdm);
            lowGridData = lowdm->getGridData(lowdm);
            gridData = dm->getGridData(dm);

            subGridData = MEM_callocN(sizeof(DMGridData*)*numGrids, "subGridData*");
            diffGrid = MEM_callocN(sizeof(DMGridData)*lowGridSize*lowGridSize, "diff");

            for(i = 0; i < numGrids; ++i) {
                /* backup subsurf grids */
                subGridData[i] = MEM_callocN(sizeof(DMGridData)*highGridSize*highGridSize, "subGridData");
                memcpy(subGridData[i], highGridData[i], sizeof(DMGridData)*highGridSize*highGridSize);

                /* write difference of subsurf and displaced low level into high subsurf */
                for(j = 0; j < lowGridSize*lowGridSize; ++j)
                    sub_v3_v3v3(diffGrid[j].co, gridData[i][j].co, lowGridData[i][j].co);

                multires_copy_dm_grid(highGridData[i], diffGrid, highGridSize, lowGridSize);
            }

            /* lower level dm no longer needed at this point */
            MEM_freeN(diffGrid);
            lowdm->release(lowdm);

            /* subsurf higher levels again with difference of coordinates */
            ss= ((CCGDerivedMesh*)highdm)->ss;
            ccgSubSurf_updateFromFaces(ss, lvl, NULL, 0);
            ccgSubSurf_updateLevels(ss, lvl, NULL, 0);

            /* add to displacements */
            multiresModifier_disp_run(highdm, me, 1, 1, subGridData, mmd->totlvl);

            /* free */
            highdm->release(highdm);
            for(i = 0; i < numGrids; ++i)
                MEM_freeN(subGridData[i]);
            MEM_freeN(subGridData);
        }
        else {
            DerivedMesh *cddm, *subdm;

            if (ob->derivedDeform) cddm = CDDM_copy(ob->derivedDeform);
            else cddm = CDDM_from_mesh(me, NULL);
            DM_set_only_copy(cddm, CD_MASK_BAREMESH);

            subdm = subsurf_dm_create_local(ob, cddm, mmd->totlvl, mmd->simple, 0, mmd->flags & eMultiresModifierFlag_PlainUv);
            cddm->release(cddm);

            multiresModifier_disp_run(dm, me, 1, 0, subdm->getGridData(subdm), mmd->totlvl);

            subdm->release(subdm);
        }
    }
}

void multires_stitch_grids(Object *ob)
{
    /* utility for smooth brush */
    if(ob && ob->derivedFinal) {
        CCGDerivedMesh *ccgdm = (CCGDerivedMesh*)ob->derivedFinal;
        CCGFace **faces;
        int totface;

        if(ccgdm->pbvh) {
            BLI_pbvh_get_grid_updates(ccgdm->pbvh, 0, (void***)&faces, &totface);

            if(totface) {
                ccgSubSurf_stitchFaces(ccgdm->ss, 0, faces, totface);
                MEM_freeN(faces);
            }
        }
    }
}

DerivedMesh *multires_dm_create_from_derived(MultiresModifierData *mmd, int local_mmd, DerivedMesh *dm, Object *ob,
                            int useRenderParams, int UNUSED(isFinalCalc))
{
    Mesh *me= ob->data;
    DerivedMesh *result;
    CCGDerivedMesh *ccgdm;
    DMGridData **gridData, **subGridData;
    int lvl= multires_get_level(ob, mmd, useRenderParams);
    int i, gridSize, numGrids;

    if(lvl == 0)
        return dm;

    result = subsurf_dm_create_local(ob, dm, lvl,
        mmd->simple, mmd->flags & eMultiresModifierFlag_ControlEdges,
        mmd->flags & eMultiresModifierFlag_PlainUv);

    if(!local_mmd) {
        ccgdm = (CCGDerivedMesh*)result;

        ccgdm->multires.ob = ob;
        ccgdm->multires.mmd = mmd;
        ccgdm->multires.local_mmd = local_mmd;
        ccgdm->multires.lvl = lvl;
        ccgdm->multires.totlvl = mmd->totlvl;
        ccgdm->multires.modified = 0;
        ccgdm->multires.update = multiresModifier_update;
    }

    numGrids = result->getNumGrids(result);
    gridSize = result->getGridSize(result);
    gridData = result->getGridData(result);

    subGridData = MEM_callocN(sizeof(DMGridData*)*numGrids, "subGridData*");

    for(i = 0; i < numGrids; i++) {
        subGridData[i] = MEM_callocN(sizeof(DMGridData)*gridSize*gridSize, "subGridData");
        memcpy(subGridData[i], gridData[i], sizeof(DMGridData)*gridSize*gridSize);
    }

    multires_set_tot_mdisps(me, mmd->totlvl);
    CustomData_external_read(&me->fdata, &me->id, CD_MASK_MDISPS, me->totface);
    multiresModifier_disp_run(result, ob->data, 0, 0, subGridData, mmd->totlvl);

    for(i = 0; i < numGrids; i++)
        MEM_freeN(subGridData[i]);
    MEM_freeN(subGridData);

    return result;
}

/**** Old Multires code ****
***************************/

/* Adapted from sculptmode.c */
void old_mdisps_bilinear(float out[3], float (*disps)[3], const int st, float u, float v)
{
    int x, y, x2, y2;
    const int st_max = st - 1;
    float urat, vrat, uopp;
    float d[4][3], d2[2][3];

    if(u < 0)
        u = 0;
    else if(u >= st)
        u = st_max;
    if(v < 0)
        v = 0;
    else if(v >= st)
        v = st_max;

    x = floor(u);
    y = floor(v);
    x2 = x + 1;
    y2 = y + 1;

    if(x2 >= st) x2 = st_max;
    if(y2 >= st) y2 = st_max;
    
    urat = u - x;
    vrat = v - y;
    uopp = 1 - urat;

    mul_v3_v3fl(d[0], disps[y * st + x], uopp);
    mul_v3_v3fl(d[1], disps[y * st + x2], urat);
    mul_v3_v3fl(d[2], disps[y2 * st + x], uopp);
    mul_v3_v3fl(d[3], disps[y2 * st + x2], urat);

    add_v3_v3v3(d2[0], d[0], d[1]);
    add_v3_v3v3(d2[1], d[2], d[3]);
    mul_v3_fl(d2[0], 1 - vrat);
    mul_v3_fl(d2[1], vrat);

    add_v3_v3v3(out, d2[0], d2[1]);
}

static void old_mdisps_rotate(int S, int UNUSED(newside), int oldside, int x, int y, float *u, float *v)
{
    float offset = oldside*0.5f - 0.5f;

    if(S == 1) { *u= offset + x; *v = offset - y; }
    if(S == 2) { *u= offset + y; *v = offset + x; }
    if(S == 3) { *u= offset - x; *v = offset + y; }
    if(S == 0) { *u= offset - y; *v = offset - x; }
}

static void old_mdisps_convert(MFace *mface, MDisps *mdisp)
{
    int newlvl = log(sqrt(mdisp->totdisp)-1)/M_LN2;
    int oldlvl = newlvl+1;
    int oldside = multires_side_tot[oldlvl];
    int newside = multires_side_tot[newlvl];
    int nvert = (mface->v4)? 4: 3;
    int newtotdisp = multires_grid_tot[newlvl]*nvert;
    int x, y, S;
    float (*disps)[3], (*out)[3], u = 0.0f, v = 0.0f; /* Quite gcc barking. */

    disps = MEM_callocN(sizeof(float) * 3 * newtotdisp, "multires disps");

    out = disps;
    for(S = 0; S < nvert; S++) {
        for(y = 0; y < newside; ++y) {
            for(x = 0; x < newside; ++x, ++out) {
                old_mdisps_rotate(S, newside, oldside, x, y, &u, &v);
                old_mdisps_bilinear(*out, mdisp->disps, oldside, u, v);

                if(S == 1) { (*out)[1]= -(*out)[1]; }
                else if(S == 2) { SWAP(float, (*out)[0], (*out)[1]); }
                else if(S == 3) { (*out)[0]= -(*out)[0]; }
                else if(S == 0) { SWAP(float, (*out)[0], (*out)[1]); (*out)[0]= -(*out)[0]; (*out)[1]= -(*out)[1]; };
            }
        }
    }

    MEM_freeN(mdisp->disps);

    mdisp->totdisp= newtotdisp;
    mdisp->disps= disps;
}

void multires_load_old_250(Mesh *me)
{
    MDisps *mdisps;
    int a;

    mdisps= CustomData_get_layer(&me->fdata, CD_MDISPS);

    if(mdisps) {
        for(a=0; a<me->totface; a++)
            if(mdisps[a].totdisp)
                old_mdisps_convert(&me->mface[a], &mdisps[a]);
    }
}

/* Does not actually free lvl itself */
static void multires_free_level(MultiresLevel *lvl)
{
    if(lvl) {
        if(lvl->faces) MEM_freeN(lvl->faces);
        if(lvl->edges) MEM_freeN(lvl->edges);
        if(lvl->colfaces) MEM_freeN(lvl->colfaces);
    }
}

void multires_free(Multires *mr)
{
    if(mr) {
        MultiresLevel* lvl= mr->levels.first;

        /* Free the first-level data */
        if(lvl) {
            CustomData_free(&mr->vdata, lvl->totvert);
            CustomData_free(&mr->fdata, lvl->totface);
            if(mr->edge_flags)
                MEM_freeN(mr->edge_flags);
            if(mr->edge_creases)
                MEM_freeN(mr->edge_creases);
        }

        while(lvl) {
            multires_free_level(lvl);           
            lvl= lvl->next;
        }

        MEM_freeN(mr->verts);

        BLI_freelistN(&mr->levels);

        MEM_freeN(mr);
    }
}

static void create_old_vert_face_map(ListBase **map, IndexNode **mem, const MultiresFace *mface,
                     const int totvert, const int totface)
{
    int i,j;
    IndexNode *node = NULL;
    
    (*map) = MEM_callocN(sizeof(ListBase) * totvert, "vert face map");
    (*mem) = MEM_callocN(sizeof(IndexNode) * totface*4, "vert face map mem");
    node = *mem;
    
    /* Find the users */
    for(i = 0; i < totface; ++i){
        for(j = 0; j < (mface[i].v[3]?4:3); ++j, ++node) {
            node->index = i;
            BLI_addtail(&(*map)[mface[i].v[j]], node);
        }
    }
}

static void create_old_vert_edge_map(ListBase **map, IndexNode **mem, const MultiresEdge *medge,
                     const int totvert, const int totedge)
{
    int i,j;
    IndexNode *node = NULL;
    
    (*map) = MEM_callocN(sizeof(ListBase) * totvert, "vert edge map");
    (*mem) = MEM_callocN(sizeof(IndexNode) * totedge*2, "vert edge map mem");
    node = *mem;
    
    /* Find the users */
    for(i = 0; i < totedge; ++i){
        for(j = 0; j < 2; ++j, ++node) {
            node->index = i;
            BLI_addtail(&(*map)[medge[i].v[j]], node);
        }
    }
}

static MultiresFace *find_old_face(ListBase *map, MultiresFace *faces, int v1, int v2, int v3, int v4)
{
    IndexNode *n1;
    int v[4], i, j;

    v[0]= v1;
    v[1]= v2;
    v[2]= v3;
    v[3]= v4;

    for(n1 = map[v1].first; n1; n1 = n1->next) {
        int fnd[4] = {0, 0, 0, 0};

        for(i = 0; i < 4; ++i) {
            for(j = 0; j < 4; ++j) {
                if(v[i] == faces[n1->index].v[j])
                    fnd[i] = 1;
            }
        }

        if(fnd[0] && fnd[1] && fnd[2] && fnd[3])
            return &faces[n1->index];
    }

    return NULL;
}

static MultiresEdge *find_old_edge(ListBase *map, MultiresEdge *edges, int v1, int v2)
{
    IndexNode *n1, *n2;

    for(n1 = map[v1].first; n1; n1 = n1->next) {
        for(n2 = map[v2].first; n2; n2 = n2->next) {
            if(n1->index == n2->index)
                return &edges[n1->index];
        }
    }

    return NULL;
}

static void multires_load_old_edges(ListBase **emap, MultiresLevel *lvl, int *vvmap, int dst, int v1, int v2, int mov)
{
    int emid = find_old_edge(emap[2], lvl->edges, v1, v2)->mid;
    vvmap[dst + mov] = emid;

    if(lvl->next->next) {
        multires_load_old_edges(emap + 1, lvl->next, vvmap, dst + mov, v1, emid, mov / 2);
        multires_load_old_edges(emap + 1, lvl->next, vvmap, dst + mov, v2, emid, -mov / 2);
    }
}

static void multires_load_old_faces(ListBase **fmap, ListBase **emap, MultiresLevel *lvl, int *vvmap, int dst,
                    int v1, int v2, int v3, int v4, int st2, int st3)
{
    int fmid;
    int emid13, emid14, emid23, emid24;

    if(lvl && lvl->next) {
        fmid = find_old_face(fmap[1], lvl->faces, v1, v2, v3, v4)->mid;
        vvmap[dst] = fmid;

        emid13 = find_old_edge(emap[1], lvl->edges, v1, v3)->mid;
        emid14 = find_old_edge(emap[1], lvl->edges, v1, v4)->mid;
        emid23 = find_old_edge(emap[1], lvl->edges, v2, v3)->mid;
        emid24 = find_old_edge(emap[1], lvl->edges, v2, v4)->mid;


        multires_load_old_faces(fmap + 1, emap + 1, lvl->next, vvmap, dst + st2 * st3 + st3,
                    fmid, v2, emid23, emid24, st2, st3 / 2);

        multires_load_old_faces(fmap + 1, emap + 1, lvl->next, vvmap, dst - st2 * st3 + st3,
                    emid14, emid24, fmid, v4, st2, st3 / 2);

        multires_load_old_faces(fmap + 1, emap + 1, lvl->next, vvmap, dst + st2 * st3 - st3,
                    emid13, emid23, v3, fmid, st2, st3 / 2);

        multires_load_old_faces(fmap + 1, emap + 1, lvl->next, vvmap, dst - st2 * st3 - st3,
                    v1, fmid, emid13, emid14, st2, st3 / 2);

        if(lvl->next->next) {
            multires_load_old_edges(emap, lvl->next, vvmap, dst, emid24, fmid, st3);
            multires_load_old_edges(emap, lvl->next, vvmap, dst, emid13, fmid, -st3);
            multires_load_old_edges(emap, lvl->next, vvmap, dst, emid14, fmid, -st2 * st3);
            multires_load_old_edges(emap, lvl->next, vvmap, dst, emid23, fmid, st2 * st3);
        }
    }
}

static void multires_mvert_to_ss(DerivedMesh *dm, MVert *mvert)
{
    CCGDerivedMesh *ccgdm = (CCGDerivedMesh*) dm;
    CCGSubSurf *ss = ccgdm->ss;
    DMGridData *vd;
    int index;
    int totvert, totedge, totface;
    int gridSize = ccgSubSurf_getGridSize(ss);
    int edgeSize = ccgSubSurf_getEdgeSize(ss);
    int i = 0;

    totface = ccgSubSurf_getNumFaces(ss);
    for(index = 0; index < totface; index++) {
        CCGFace *f = ccgdm->faceMap[index].face;
        int x, y, S, numVerts = ccgSubSurf_getFaceNumVerts(f);

        vd= ccgSubSurf_getFaceCenterData(f);
        copy_v3_v3(vd->co, mvert[i].co);
        i++;
        
        for(S = 0; S < numVerts; S++) {
            for(x = 1; x < gridSize - 1; x++, i++) {
                vd= ccgSubSurf_getFaceGridEdgeData(ss, f, S, x);
                copy_v3_v3(vd->co, mvert[i].co);
            }
        }

        for(S = 0; S < numVerts; S++) {
            for(y = 1; y < gridSize - 1; y++) {
                for(x = 1; x < gridSize - 1; x++, i++) {
                    vd= ccgSubSurf_getFaceGridData(ss, f, S, x, y);
                    copy_v3_v3(vd->co, mvert[i].co);
                }
            }
        }
    }

    totedge = ccgSubSurf_getNumEdges(ss);
    for(index = 0; index < totedge; index++) {
        CCGEdge *e = ccgdm->edgeMap[index].edge;
        int x;

        for(x = 1; x < edgeSize - 1; x++, i++) {
            vd= ccgSubSurf_getEdgeData(ss, e, x);
            copy_v3_v3(vd->co, mvert[i].co);
        }
    }

    totvert = ccgSubSurf_getNumVerts(ss);
    for(index = 0; index < totvert; index++) {
        CCGVert *v = ccgdm->vertMap[index].vert;

        vd= ccgSubSurf_getVertData(ss, v);
        copy_v3_v3(vd->co, mvert[i].co);
        i++;
    }

    ccgSubSurf_updateToFaces(ss, 0, NULL, 0);
}

/* Loads a multires object stored in the old Multires struct into the new format */
static void multires_load_old_dm(DerivedMesh *dm, Mesh *me, int totlvl)
{
    MultiresLevel *lvl, *lvl1;
    Multires *mr= me->mr;
    MVert *vsrc, *vdst;
    unsigned int src, dst;
    int st = multires_side_tot[totlvl - 1] - 1;
    int extedgelen = multires_side_tot[totlvl] - 2;
    int *vvmap; // inorder for dst, map to src
    int crossedgelen;
    int s, x, tottri, totquad;
    unsigned int i, j, totvert;

    src = 0;
    vsrc = mr->verts;
    vdst = dm->getVertArray(dm);
    totvert = (unsigned int)dm->getNumVerts(dm);
    vvmap = MEM_callocN(sizeof(int) * totvert, "multires vvmap");

    lvl1 = mr->levels.first;
    /* Load base verts */
    for(i = 0; i < lvl1->totvert; ++i) {
        vvmap[totvert - lvl1->totvert + i] = src;
        ++src;
    }

    /* Original edges */
    dst = totvert - lvl1->totvert - extedgelen * lvl1->totedge;
    for(i = 0; i < lvl1->totedge; ++i) {
        int ldst = dst + extedgelen * i;
        int lsrc = src;
        lvl = lvl1->next;

        for(j = 2; j <= mr->level_count; ++j) {
            int base = multires_side_tot[totlvl - j + 1] - 2;
            int skip = multires_side_tot[totlvl - j + 2] - 1;
            int st = multires_side_tot[j - 1] - 1;

            for(x = 0; x < st; ++x)
                vvmap[ldst + base + x * skip] = lsrc + st * i + x;

            lsrc += lvl->totvert - lvl->prev->totvert;
            lvl = lvl->next;
        }
    }

    /* Center points */
    dst = 0;
    for(i = 0; i < lvl1->totface; ++i) {
        int sides = lvl1->faces[i].v[3] ? 4 : 3;

        vvmap[dst] = src + lvl1->totedge + i;
        dst += 1 + sides * (st - 1) * st;
    }


    /* The rest is only for level 3 and up */
    if(lvl1->next && lvl1->next->next) {
        ListBase **fmap, **emap;
        IndexNode **fmem, **emem;

        /* Face edge cross */
        tottri = totquad = 0;
        crossedgelen = multires_side_tot[totlvl - 1] - 2;
        dst = 0;
        for(i = 0; i < lvl1->totface; ++i) {
            int sides = lvl1->faces[i].v[3] ? 4 : 3;

            lvl = lvl1->next->next;
            ++dst;

            for(j = 3; j <= mr->level_count; ++j) {
                int base = multires_side_tot[totlvl - j + 1] - 2;
                int skip = multires_side_tot[totlvl - j + 2] - 1;
                int st = pow(2, j - 2);
                int st2 = pow(2, j - 3);
                int lsrc = lvl->prev->totvert;

                /* Skip exterior edge verts */
                lsrc += lvl1->totedge * st;

                /* Skip earlier face edge crosses */
                lsrc += st2 * (tottri * 3 + totquad * 4);

                for(s = 0; s < sides; ++s) {
                    for(x = 0; x < st2; ++x) {
                        vvmap[dst + crossedgelen * (s + 1) - base - x * skip - 1] = lsrc;
                        ++lsrc;
                    }
                }

                lvl = lvl->next;
            }

            dst += sides * (st - 1) * st;

            if(sides == 4) ++totquad;
            else ++tottri;

        }

        /* calculate vert to edge/face maps for each level (except the last) */
        fmap = MEM_callocN(sizeof(ListBase*) * (mr->level_count-1), "multires fmap");
        emap = MEM_callocN(sizeof(ListBase*) * (mr->level_count-1), "multires emap");
        fmem = MEM_callocN(sizeof(IndexNode*) * (mr->level_count-1), "multires fmem");
        emem = MEM_callocN(sizeof(IndexNode*) * (mr->level_count-1), "multires emem");
        lvl = lvl1;
        for(i = 0; i < (unsigned int)mr->level_count - 1; ++i) {
            create_old_vert_face_map(fmap + i, fmem + i, lvl->faces, lvl->totvert, lvl->totface);
            create_old_vert_edge_map(emap + i, emem + i, lvl->edges, lvl->totvert, lvl->totedge);
            lvl = lvl->next;
        }

        /* Interior face verts */
        /* lvl = lvl1->next->next; */ /* UNUSED */
        dst = 0;
        for(j = 0; j < lvl1->totface; ++j) {
            int sides = lvl1->faces[j].v[3] ? 4 : 3;
            int ldst = dst + 1 + sides * (st - 1);

            for(s = 0; s < sides; ++s) {
                int st2 = multires_side_tot[totlvl - 1] - 2;
                int st3 = multires_side_tot[totlvl - 2] - 2;
                int st4 = st3 == 0 ? 1 : (st3 + 1) / 2;
                int mid = ldst + st2 * st3 + st3;
                int cv = lvl1->faces[j].v[s];
                int nv = lvl1->faces[j].v[s == sides - 1 ? 0 : s + 1];
                int pv = lvl1->faces[j].v[s == 0 ? sides - 1 : s - 1];

                multires_load_old_faces(fmap, emap, lvl1->next, vvmap, mid,
                            vvmap[dst], cv,
                            find_old_edge(emap[0], lvl1->edges, pv, cv)->mid,
                            find_old_edge(emap[0], lvl1->edges, cv, nv)->mid,
                            st2, st4);

                ldst += (st - 1) * (st - 1);
            }


            dst = ldst;
        }

        /*lvl = lvl->next;*/ /*UNUSED*/

        for(i = 0; i < (unsigned int)(mr->level_count - 1); ++i) {
            MEM_freeN(fmap[i]);
            MEM_freeN(fmem[i]);
            MEM_freeN(emap[i]);
            MEM_freeN(emem[i]);
        }

        MEM_freeN(fmap);
        MEM_freeN(emap);
        MEM_freeN(fmem);
        MEM_freeN(emem);
    }

    /* Transfer verts */
    for(i = 0; i < totvert; ++i)
        copy_v3_v3(vdst[i].co, vsrc[vvmap[i]].co);

    MEM_freeN(vvmap);

    multires_mvert_to_ss(dm, vdst);
}

/* Copy the first-level vcol data to the mesh, if it exists */
/* Warning: higher-level vcol data will be lost */
static void multires_load_old_vcols(Mesh *me)
{
    MultiresLevel *lvl;
    MultiresColFace *colface;
    MCol *mcol;
    int i, j;

    if(!(lvl = me->mr->levels.first))
        return;

    if(!(colface = lvl->colfaces))
        return;

    /* older multires format never supported multiple vcol layers,
       so we can assume the active vcol layer is the correct one */
    if(!(mcol = CustomData_get_layer(&me->fdata, CD_MCOL)))
        return;
    
    for(i = 0; i < me->totface; ++i) {
        for(j = 0; j < 4; ++j) {
            mcol[i*4 + j].a = colface[i].col[j].a;
            mcol[i*4 + j].r = colface[i].col[j].r;
            mcol[i*4 + j].g = colface[i].col[j].g;
            mcol[i*4 + j].b = colface[i].col[j].b;
        }
    }
}

/* Copy the first-level face-flag data to the mesh */
static void multires_load_old_face_flags(Mesh *me)
{
    MultiresLevel *lvl;
    MultiresFace *faces;
    int i;

    if(!(lvl = me->mr->levels.first))
        return;

    if(!(faces = lvl->faces))
        return;

    for(i = 0; i < me->totface; ++i)
        me->mface[i].flag = faces[i].flag;
}

void multires_load_old(Object *ob, Mesh *me)
{
    MultiresLevel *lvl;
    ModifierData *md;
    MultiresModifierData *mmd;
    DerivedMesh *dm, *orig;
    CustomDataLayer *l;
    int i;

    /* Load original level into the mesh */
    lvl = me->mr->levels.first;
    CustomData_free_layers(&me->vdata, CD_MVERT, lvl->totvert);
    CustomData_free_layers(&me->edata, CD_MEDGE, lvl->totedge);
    CustomData_free_layers(&me->fdata, CD_MFACE, lvl->totface);
    me->totvert = lvl->totvert;
    me->totedge = lvl->totedge;
    me->totface = lvl->totface;
    me->mvert = CustomData_add_layer(&me->vdata, CD_MVERT, CD_CALLOC, NULL, me->totvert);
    me->medge = CustomData_add_layer(&me->edata, CD_MEDGE, CD_CALLOC, NULL, me->totedge);
    me->mface = CustomData_add_layer(&me->fdata, CD_MFACE, CD_CALLOC, NULL, me->totface);
    memcpy(me->mvert, me->mr->verts, sizeof(MVert) * me->totvert);
    for(i = 0; i < me->totedge; ++i) {
        me->medge[i].v1 = lvl->edges[i].v[0];
        me->medge[i].v2 = lvl->edges[i].v[1];
    }
    for(i = 0; i < me->totface; ++i) {
        me->mface[i].v1 = lvl->faces[i].v[0];
        me->mface[i].v2 = lvl->faces[i].v[1];
        me->mface[i].v3 = lvl->faces[i].v[2];
        me->mface[i].v4 = lvl->faces[i].v[3];
        me->mface[i].mat_nr = lvl->faces[i].mat_nr;
    }

    /* Add a multires modifier to the object */
    md = ob->modifiers.first;
    while(md && modifierType_getInfo(md->type)->type == eModifierTypeType_OnlyDeform)
        md = md->next;                          
    mmd = (MultiresModifierData*)modifier_new(eModifierType_Multires);
    BLI_insertlinkbefore(&ob->modifiers, md, mmd);

    for(i = 0; i < me->mr->level_count - 1; ++i)
        multiresModifier_subdivide(mmd, ob, 1, 0);

    mmd->lvl = mmd->totlvl;
    orig = CDDM_from_mesh(me, NULL);
    dm = multires_dm_create_from_derived(mmd, 0, orig, ob, 0, 0);
                       
    multires_load_old_dm(dm, me, mmd->totlvl+1);

    multires_dm_mark_as_modified(dm);
    dm->release(dm);
    orig->release(orig);

    /* Copy the first-level data to the mesh */
    for(i = 0, l = me->mr->vdata.layers; i < me->mr->vdata.totlayer; ++i, ++l)
        CustomData_add_layer(&me->vdata, l->type, CD_REFERENCE, l->data, me->totvert);
    for(i = 0, l = me->mr->fdata.layers; i < me->mr->fdata.totlayer; ++i, ++l)
        CustomData_add_layer(&me->fdata, l->type, CD_REFERENCE, l->data, me->totface);
    memset(&me->mr->vdata, 0, sizeof(CustomData));
    memset(&me->mr->fdata, 0, sizeof(CustomData));

    multires_load_old_vcols(me);
    multires_load_old_face_flags(me);

    /* Remove the old multires */
    multires_free(me->mr);
    me->mr= NULL;
}

static void multires_sync_levels(Scene *scene, Object *ob, Object *to_ob)
{
    MultiresModifierData *mmd= get_multires_modifier(scene, ob, 1);
    MultiresModifierData *to_mmd= get_multires_modifier(scene, to_ob, 1);

    if(!mmd) {
        /* object could have MDISP even when there is no multires modifier
           this could lead to troubles due to i've got no idea how mdisp could be
           upsampled correct without modifier data.
           just remove mdisps if no multires present (nazgul) */

        Mesh *me= (Mesh*)ob->data;

        CustomData_external_remove(&me->fdata, &me->id, CD_MDISPS, me->totface);
        CustomData_free_layer_active(&me->fdata, CD_MDISPS, me->totface);
    }

    if(!mmd || !to_mmd) return;

    if(mmd->totlvl>to_mmd->totlvl) multires_del_higher(mmd, ob, to_mmd->totlvl);
    else multires_subdivide(mmd, ob, to_mmd->totlvl, 0, mmd->simple);
}

static void multires_apply_smat(Scene *scene, Object *ob, float smat[3][3])
{
    DerivedMesh *dm= NULL, *cddm= NULL, *subdm= NULL;
    DMGridData **gridData, **subGridData;
    Mesh *me= (Mesh*)ob->data;
    MFace *mface= me->mface;
    MDisps *mdisps;
    int *gridOffset;
    int i, /*numGrids,*/ gridSize, dGridSize, dSkip, totvert;
    float (*vertCos)[3] = NULL;
    MultiresModifierData *mmd= get_multires_modifier(scene, ob, 1);
    MultiresModifierData high_mmd;

    CustomData_external_read(&me->fdata, &me->id, CD_MASK_MDISPS, me->totface);
    mdisps= CustomData_get_layer(&me->fdata, CD_MDISPS);

    if(!mdisps || !mmd || !mmd->totlvl) return;

    /* we need derived mesh created from highest resolution */
    high_mmd= *mmd;
    high_mmd.lvl= high_mmd.totlvl;

    /* unscaled multires with applied displacement */
    subdm= get_multires_dm(scene, &high_mmd, ob);

    /* prepare scaled CDDM to create ccgDN */
    cddm= mesh_get_derived_deform(scene, ob, CD_MASK_BAREMESH);

    totvert= cddm->getNumVerts(cddm);
    vertCos= MEM_mallocN(sizeof(*vertCos) * totvert, "multiresScale vertCos");
    cddm->getVertCos(cddm, vertCos);
    for(i=0; i<totvert; i++)
        mul_m3_v3(smat, vertCos[i]);
    CDDM_apply_vert_coords(cddm, vertCos);
    MEM_freeN(vertCos);

    /* scaled ccgDM for tangent space of object with applied scale */
    dm= subsurf_dm_create_local(ob, cddm, high_mmd.totlvl, high_mmd.simple, 0, mmd->flags & eMultiresModifierFlag_PlainUv);
    cddm->release(cddm);

    /*numGrids= dm->getNumGrids(dm);*/ /*UNUSED*/
    gridSize= dm->getGridSize(dm);
    gridData= dm->getGridData(dm);
    gridOffset= dm->getGridOffset(dm);
    subGridData= subdm->getGridData(subdm);

    dGridSize= multires_side_tot[high_mmd.totlvl];
    dSkip= (dGridSize-1)/(gridSize-1);

    #pragma omp parallel for private(i) if(me->totface*gridSize*gridSize*4 >= CCG_OMP_LIMIT)
    for(i = 0; i < me->totface; ++i) {
        const int numVerts= mface[i].v4 ? 4 : 3;
        MDisps *mdisp= &mdisps[i];
        int S, x, y, gIndex = gridOffset[i];

        for(S = 0; S < numVerts; ++S, ++gIndex) {
            DMGridData *grid= gridData[gIndex];
            DMGridData *subgrid= subGridData[gIndex];
            float (*dispgrid)[3]= &mdisp->disps[S*dGridSize*dGridSize];

            for(y = 0; y < gridSize; y++) {
                for(x = 0; x < gridSize; x++) {
                    float *co= grid[x + y*gridSize].co;
                    float *sco= subgrid[x + y*gridSize].co;
                    float *no= grid[x + y*gridSize].no;
                    float *data= dispgrid[dGridSize*y*dSkip + x*dSkip];
                    float mat[3][3], tx[3], ty[3], disp[3];

                    /* construct tangent space matrix */
                    grid_tangent(gridSize, gIndex, x, y, 0, gridData, tx);
                    normalize_v3(tx);

                    grid_tangent(gridSize, gIndex, x, y, 1, gridData, ty);
                    normalize_v3(ty);

                    column_vectors_to_mat3(mat, tx, ty, no);

                    /* scale subgrid coord and calculate displacement */
                    mul_m3_v3(smat, sco);
                    sub_v3_v3v3(disp, sco, co);

                    /* convert difference to tangent space */
                    invert_m3(mat);
                    mul_v3_m3v3(data, mat, disp);
                }
            }
        }
    }

    dm->release(dm);
    subdm->release(subdm);
}

int multires_mdisp_corners(MDisps *s)
{
    int lvl= 13;

    while(lvl > 0) {
        int side = (1 << (lvl-1)) + 1;
        if ((s->totdisp % (side*side)) == 0) return s->totdisp / (side*side);
        lvl--;
    }

    return 0;
}

void multiresModifier_scale_disp(Scene *scene, Object *ob)
{
    float smat[3][3];

    /* object's scale matrix */
    object_scale_to_mat3(ob, smat);

    multires_apply_smat(scene, ob, smat);
}

void multiresModifier_prepare_join(Scene *scene, Object *ob, Object *to_ob)
{
    float smat[3][3], tmat[3][3], mat[3][3];
    multires_sync_levels(scene, ob, to_ob);

    /* construct scale matrix for displacement */
    object_scale_to_mat3(to_ob, tmat);
    invert_m3(tmat);
    object_scale_to_mat3(ob, smat);
    mul_m3_m3m3(mat, smat, tmat);

    multires_apply_smat(scene, ob, mat);
}

/* update multires data after topology changing */
void multires_topology_changed(Scene *scene, Object *ob)
{
    Mesh *me= (Mesh*)ob->data;
    MDisps *mdisp= NULL, *cur= NULL;
    int i, grid= 0, corners;
    MultiresModifierData *mmd= get_multires_modifier(scene, ob, 1);

    if(mmd)
        multires_set_tot_mdisps(me, mmd->totlvl);

    CustomData_external_read(&me->fdata, &me->id, CD_MASK_MDISPS, me->totface);
    mdisp= CustomData_get_layer(&me->fdata, CD_MDISPS);

    if(!mdisp) return;

    cur= mdisp;
    for(i = 0; i < me->totface; i++, cur++) {
        if(mdisp->totdisp) {
            corners= multires_mdisp_corners(mdisp);
            grid= mdisp->totdisp / corners;

            break;
        }
    }

    for(i = 0; i < me->totface; i++, mdisp++) {
        int nvert= me->mface[i].v4 ? 4 : 3;

        /* allocate memory for mdisp, the whole disp layer would be erased otherwise */
        if(!mdisp->totdisp || !mdisp->disps) {
            if(grid) {
                mdisp->totdisp= nvert*grid;
                mdisp->disps= MEM_callocN(mdisp->totdisp*sizeof(float)*3, "mdisp topology");
            }

            continue;
        }

        corners= multires_mdisp_corners(mdisp);

        if(corners!=nvert) {
            mdisp->totdisp= (mdisp->totdisp/corners)*nvert;

            if(mdisp->disps)
                MEM_freeN(mdisp->disps);

            mdisp->disps= MEM_callocN(mdisp->totdisp*sizeof(float)*3, "mdisp topology");
        }
    }
}

/* makes displacement along grid boundary symmetrical */
void multires_mdisp_smooth_bounds(MDisps *disps)
{
    int x, y, side, S, corners;
    float (*out)[3];

    corners = multires_mdisp_corners(disps);
    side = sqrt(disps->totdisp / corners);

    out = disps->disps;
    for(S = 0; S < corners; S++) {
        for(y = 0; y < side; ++y) {
            for(x = 0; x < side; ++x, ++out) {
                float (*dispgrid)[3];
                float *data;

                if(x != 0 && y != 0) continue;

                if(corners == 4) {
                    if(S == 0) {
                        if(y == 0) {
                            dispgrid = &disps->disps[1*side*side];
                            data = dispgrid[side * x + 0];

                            (*out)[0] = (*out)[0] + data[1];
                            (*out)[1] = (*out)[1] - data[0];
                            (*out)[2] = (*out)[2] + data[2];

                            mul_v3_fl(*out, 0.5);

                            data[0] = -(*out)[1];
                            data[1] = (*out)[0];
                            data[2] = (*out)[2];
                        } else if (x == 0) {
                            dispgrid = &disps->disps[3 * side * side];
                            data = dispgrid[side * 0 + y];

                            (*out)[0] = (*out)[0] - data[1];
                            (*out)[1] = (*out)[1] + data[0];
                            (*out)[2] = (*out)[2] + data[2];

                            mul_v3_fl(*out, 0.5);

                            data[0] = (*out)[1];
                            data[1] = -(*out)[0];
                            data[2] = (*out)[2];
                        }
                    } else if (S == 2) {
                        if(y == 0) {
                            dispgrid = &disps->disps[3 * side * side];
                            data = dispgrid[side * x + 0];

                            (*out)[0] = (*out)[0] + data[1];
                            (*out)[1] = (*out)[1] - data[0];
                            (*out)[2] = (*out)[2] + data[2];

                            mul_v3_fl(*out, 0.5);

                            data[0] = -(*out)[1];
                            data[1] = (*out)[0];
                            data[2] = (*out)[2];
                        } else if(x == 0) {
                            dispgrid = &disps->disps[1 * side * side];
                            data = dispgrid[side * 0 + y];

                            (*out)[0] = (*out)[0] - data[1];
                            (*out)[1] = (*out)[1] + data[0];
                            (*out)[2] = (*out)[2] + data[2];

                            mul_v3_fl(*out, 0.5);

                            data[0] = (*out)[1];
                            data[1] = -(*out)[0];
                            data[2] = (*out)[2];
                        }
                    }
                } else if (corners == 3) {
                    if(S == 0) {
                        if(y == 0) {
                            dispgrid = &disps->disps[1*side*side];
                            data = dispgrid[side * x + 0];

                            (*out)[0] = (*out)[0] + data[1];
                            (*out)[1] = (*out)[1] - data[0];
                            (*out)[2] = (*out)[2] + data[2];

                            mul_v3_fl(*out, 0.5);

                            data[0] = -(*out)[1];
                            data[1] = (*out)[0];
                            data[2] = (*out)[2];
                        } else if (x == 0) {
                            dispgrid = &disps->disps[2 * side * side];
                            data = dispgrid[side * 0 + y];

                            (*out)[0] = (*out)[0] - data[1];
                            (*out)[1] = (*out)[1] + data[0];
                            (*out)[2] = (*out)[2] + data[2];

                            mul_v3_fl(*out, 0.5);

                            data[0] = (*out)[1];
                            data[1] = -(*out)[0];
                            data[2] = (*out)[2];
                        }
                    } else if (S == 2) {
                        if(x == 0) {
                            dispgrid = &disps->disps[1 * side * side];
                            data = dispgrid[side * 0 + y];

                            (*out)[0] = (*out)[0] - data[1];
                            (*out)[1] = (*out)[1] + data[0];
                            (*out)[2] = (*out)[2] + data[2];

                            mul_v3_fl(*out, 0.5);

                            data[0] = (*out)[1];
                            data[1] = -(*out)[0];
                            data[2] = (*out)[2];
                        }
                    }
                }
            }
        }
    }
}

/***************** Multires interpolation stuff *****************/

static void mdisp_get_crn_rect(int face_side, float crn[3][4][2])
{
    float offset = face_side*0.5f - 0.5f;
    float mid[2];

    mid[0] = offset * 4 / 3;
    mid[1] = offset * 2 / 3;

    crn[0][0][0] = mid[0]; crn[0][0][1] = mid[1];
    crn[0][1][0] = offset; crn[0][1][1] = 0;
    crn[0][2][0] = 0; crn[0][2][1] = 0;
    crn[0][3][0] = offset; crn[0][3][1] = offset;

    crn[1][0][0] = mid[0]; crn[1][0][1] = mid[1];
    crn[1][1][0] = offset * 2; crn[1][1][1] = offset;
    crn[1][2][0] = offset * 2; crn[1][2][1] = 0;
    crn[1][3][0] = offset; crn[1][3][1] = 0;

    crn[2][0][0] = mid[0]; crn[2][0][1] = mid[1];
    crn[2][1][0] = offset; crn[2][1][1] = offset;
    crn[2][2][0] = offset * 2; crn[2][2][1] = offset * 2;
    crn[2][3][0] = offset * 2; crn[2][3][1] = offset;
}

static int mdisp_pt_in_crn(float p[2], float crn[4][2])
{
    float v[2][2];
    float a[2][2];

    sub_v2_v2v2(v[0], crn[1], crn[0]);
    sub_v2_v2v2(v[1], crn[3], crn[0]);

    sub_v2_v2v2(a[0], p, crn[0]);
    sub_v2_v2v2(a[1], crn[2], crn[0]);

    if(cross_v2v2(a[0], v[0]) * cross_v2v2(a[1], v[0]) < 0)
        return 0;

    if(cross_v2v2(a[0], v[1]) * cross_v2v2(a[1], v[1]) < 0)
        return 0;

    return 1;
}

static void face_to_crn_interp(float u, float v, float v1[2], float v2[2], float v3[2], float v4[2], float *x)
{
    float a = (v4[1]-v3[1])*v2[0]+(-v4[1]+v3[1])*v1[0]+(-v2[1]+v1[1])*v4[0]+(v2[1]-v1[1])*v3[0];
    float b = (v3[1]-v)*v2[0]+(v4[1]-2*v3[1]+v)*v1[0]+(-v4[1]+v3[1]+v2[1]-v1[1])*u+(v4[0]-v3[0])*v-v1[1]*v4[0]+(-v2[1]+2*v1[1])*v3[0];
    float c = (v3[1]-v)*v1[0]+(-v3[1]+v1[1])*u+v3[0]*v-v1[1]*v3[0];
    float d = b * b - 4 * a * c;
    float x1, x2;

    if(a == 0) {
        *x = -c / b;
        return;
    }

    x1 = (-b - sqrtf(d)) / (2 * a);
    x2 = (-b + sqrtf(d)) / (2 * a);

    *x = maxf(x1, x2);
}

void mdisp_rot_crn_to_face(const int S, const int corners, const int face_side, const float x, const float y, float *u, float *v)
{
    float offset = face_side*0.5f - 0.5f;

    if(corners == 4) {
        if(S == 1) { *u= offset + x; *v = offset - y; }
        if(S == 2) { *u= offset + y; *v = offset + x; }
        if(S == 3) { *u= offset - x; *v = offset + y; }
        if(S == 0) { *u= offset - y; *v = offset - x; }
    } else {
        float crn[3][4][2], vec[4][2];
        float p[2];

        mdisp_get_crn_rect(face_side, crn);

        interp_v2_v2v2(vec[0], crn[S][0], crn[S][1], x / offset);
        interp_v2_v2v2(vec[1], crn[S][3], crn[S][2], x / offset);
        interp_v2_v2v2(vec[2], crn[S][0], crn[S][3], y / offset);
        interp_v2_v2v2(vec[3], crn[S][1], crn[S][2], y / offset);

        isect_seg_seg_v2_point(vec[0], vec[1], vec[2], vec[3], p);

        (*u) = p[0];
        (*v) = p[1];
    }
}

/* Find per-corner coordinate with given per-face UV coord */
int mdisp_rot_face_to_crn(const int corners, const int face_side, const float u, const float v, float *x, float *y)
{
    const float offset = face_side*0.5f - 0.5f;
    int S = 0;

    if (corners == 4) {
        if(u <= offset && v <= offset) S = 0;
        else if(u > offset  && v <= offset) S = 1;
        else if(u > offset  && v > offset) S = 2;
        else if(u <= offset && v >= offset)  S = 3;

        if(S == 0) {
            *y = offset - u;
            *x = offset - v;
        } else if(S == 1) {
            *x = u - offset;
            *y = offset - v;
        } else if(S == 2) {
            *y = u - offset;
            *x = v - offset;
        } else if(S == 3) {
            *x= offset - u;
            *y = v - offset;
        }
    } else {
        int grid_size = offset;
        float w = (face_side - 1) - u - v;
        float W1, W2;

        if (u >= v && u >= w) {S = 0; W1= w; W2= v;}
        else if (v >= u && v >= w) {S = 1; W1 = u; W2 = w;}
        else {S = 2; W1 = v; W2 = u;}

        W1 /= (face_side-1);
        W2 /= (face_side-1);

        *x = (1-(2*W1)/(1-W2)) * grid_size;
        *y = (1-(2*W2)/(1-W1)) * grid_size;
    }

    return S;
}

/* Find per-corner coordinate with given per-face UV coord
   Practically as the previous funciton but it assumes a bit different coordinate system for triangles
   which is optimized for MDISP layer interpolation:

   v
   ^
   |      /|
   |    /  |
   |  /    |
   |/______|___> u

 */
int mdisp_rot_face_to_quad_crn(const int corners, const int face_side, const float u, const float v, float *x, float *y)
{
    const float offset = face_side*0.5f - 0.5f;
    int S = 0;

    if (corners == 4) {
        if(u <= offset && v <= offset) S = 0;
        else if(u > offset  && v <= offset) S = 1;
        else if(u > offset  && v > offset) S = 2;
        else if(u <= offset && v >= offset)  S = 3;

        if(S == 0) {
            *y = offset - u;
            *x = offset - v;
        } else if(S == 1) {
            *x = u - offset;
            *y = offset - v;
        } else if(S == 2) {
            *y = u - offset;
            *x = v - offset;
        } else if(S == 3) {
            *x= offset - u;
            *y = v - offset;
        }
    } else {
        float crn[3][4][2];
        float p[2] = {u, v};

        mdisp_get_crn_rect(face_side, crn);

        for (S = 0; S < 3; ++S) {
            if (mdisp_pt_in_crn(p, crn[S]))
                break;
        }

        face_to_crn_interp(u, v, crn[S][0], crn[S][1], crn[S][3], crn[S][2], &p[0]);
        face_to_crn_interp(u, v, crn[S][0], crn[S][3], crn[S][1], crn[S][2], &p[1]);

        *x = p[0] * offset;
        *y = p[1] * offset;
    }

    return S;
}

void mdisp_apply_weight(const int S, const int corners, int x, int y, const int face_side,
    float crn_weight[4][2], float *u_r, float *v_r)
{
    float u, v, xl, yl;
    float mid1[2], mid2[2], mid3[2];

    mdisp_rot_crn_to_face(S, corners, face_side, x, y, &u, &v);

    if(corners == 4) {
        xl = u / (face_side - 1);
        yl = v / (face_side - 1);

        mid1[0] = crn_weight[0][0] * (1 - xl) + crn_weight[1][0] * xl;
        mid1[1] = crn_weight[0][1] * (1 - xl) + crn_weight[1][1] * xl;
        mid2[0] = crn_weight[3][0] * (1 - xl) + crn_weight[2][0] * xl;
        mid2[1] = crn_weight[3][1] * (1 - xl) + crn_weight[2][1] * xl;
        mid3[0] = mid1[0] * (1 - yl) + mid2[0] * yl;
        mid3[1] = mid1[1] * (1 - yl) + mid2[1] * yl;
    } else {
        yl = v / (face_side - 1);

        if(v == face_side - 1) xl = 1;
        else xl = 1 - (face_side - 1 - u) / (face_side - 1 - v);

        mid1[0] = crn_weight[0][0] * (1 - xl) + crn_weight[1][0] * xl;
        mid1[1] = crn_weight[0][1] * (1 - xl) + crn_weight[1][1] * xl;
        mid3[0] = mid1[0] * (1 - yl) + crn_weight[2][0] * yl;
        mid3[1] = mid1[1] * (1 - yl) + crn_weight[2][1] * yl;
    }

    *u_r = mid3[0];
    *v_r = mid3[1];
}

void mdisp_flip_disp(const int S, const int corners, const float axis_x[2], const float axis_y[2], float disp[3])
{
    float crn_x[2], crn_y[2];
    float vx[2], vy[2], coord[2];

    if (corners == 4) {
        float x[4][2] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}};
        float y[4][2] = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};

        copy_v2_v2(crn_x, x[S]);
        copy_v2_v2(crn_y, y[S]);

        mul_v2_v2fl(vx, crn_x, disp[0]);
        mul_v2_v2fl(vy, crn_y, disp[1]);
        add_v2_v2v2(coord, vx, vy);

        project_v2_v2v2(vx, coord, axis_x);
        project_v2_v2v2(vy, coord, axis_y);

        disp[0] = len_v2(vx);
        disp[1] = len_v2(vy);

        if(dot_v2v2(vx, axis_x) < 0)
            disp[0] = -disp[0];

        if(dot_v2v2(vy, axis_y) < 0)
            disp[1] = -disp[1];
    } else {
        /* XXX: it was very overhead code to support displacement flipping
                for case of tris without visible profit.
                Maybe its not really big limitation? for now? (nazgul) */
        disp[0] = 0;
        disp[1] = 0;
    }
}

/* Join two triangular displacements into one quad
     Corners mapping:
     2 -------- 3
     | \   tri2 |
     |    \     |
     | tri1  \  |
     0 -------- 1 */
void mdisp_join_tris(MDisps *dst, MDisps *tri1, MDisps *tri2)
{
    int side, st;
    int S, x, y, crn;
    float face_u, face_v, crn_u, crn_v;
    float (*out)[3];
    MDisps *src;

    if(dst->disps)
        MEM_freeN(dst->disps);

    side = sqrt(tri1->totdisp / 3);
    st = (side<<1)-1;

    dst->totdisp = 4 * side * side;
    out = dst->disps = MEM_callocN(3*dst->totdisp*sizeof(float), "join disps");

    for(S = 0; S < 4; S++)
        for(y = 0; y < side; ++y)
            for(x = 0; x < side; ++x, ++out) {
                mdisp_rot_crn_to_face(S, 4, st, x, y, &face_u, &face_v);
                face_u = st - 1 - face_u;

                if(face_v > face_u) {
                    src = tri2;
                    face_u = st - 1 - face_u;
                    face_v = st - 1 - face_v;
                } else src = tri1;

                crn = mdisp_rot_face_to_quad_crn(3, st, face_u, face_v, &crn_u, &crn_v);

                old_mdisps_bilinear((*out), &src->disps[crn*side*side], side, crn_u, crn_v);
                (*out)[0] = 0;
                (*out)[1] = 0;
            }
}