strand.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) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 *
 * The Original Code is: none of this file.
 *
 * Contributors: Brecht Van Lommel.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

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

#include "MEM_guardedalloc.h"

#include "DNA_key_types.h"
#include "DNA_material_types.h"
#include "DNA_meshdata_types.h"

#include "BLI_math.h"
#include "BLI_blenlib.h"
#include "BLI_utildefines.h"
#include "BLI_ghash.h"
#include "BLI_memarena.h"
#include "BLI_rand.h"

#include "BKE_DerivedMesh.h"
#include "BKE_key.h"


#include "render_types.h"
#include "initrender.h"
#include "rendercore.h"
#include "renderdatabase.h"
#include "renderpipeline.h"
#include "pixelblending.h"
#include "shading.h"
#include "strand.h"
#include "zbuf.h"

/* to be removed */
void hoco_to_zco(ZSpan *zspan, float *zco, float *hoco);
void zspan_scanconvert_strand(ZSpan *zspan, void *handle, float *v1, float *v2, float *v3, void (*func)(void *, int, int, float, float, float) );
void zbufsinglewire(ZSpan *zspan, int obi, int zvlnr, float *ho1, float *ho2);

/* *************** */

static float strand_eval_width(Material *ma, float strandco)
{
    float fac;

    strandco= 0.5f*(strandco + 1.0f);

    if(ma->strand_ease!=0.0f) {
        if(ma->strand_ease<0.0f)
            fac= pow(strandco, 1.0f+ma->strand_ease);
        else
            fac= pow(strandco, 1.0f/(1.0f-ma->strand_ease));
    }
    else fac= strandco;
    
    return ((1.0f-fac)*ma->strand_sta + (fac)*ma->strand_end);
}

void strand_eval_point(StrandSegment *sseg, StrandPoint *spoint)
{
    Material *ma;
    StrandBuffer *strandbuf;
    float *simplify;
    float p[4][3], data[4], cross[3], w, dx, dy, t;
    int type;

    strandbuf= sseg->buffer;
    ma= sseg->buffer->ma;
    t= spoint->t;
    type= (strandbuf->flag & R_STRAND_BSPLINE)? KEY_BSPLINE: KEY_CARDINAL;

    copy_v3_v3(p[0], sseg->v[0]->co);
    copy_v3_v3(p[1], sseg->v[1]->co);
    copy_v3_v3(p[2], sseg->v[2]->co);
    copy_v3_v3(p[3], sseg->v[3]->co);

    if(sseg->obi->flag & R_TRANSFORMED) {
        mul_m4_v3(sseg->obi->mat, p[0]);
        mul_m4_v3(sseg->obi->mat, p[1]);
        mul_m4_v3(sseg->obi->mat, p[2]);
        mul_m4_v3(sseg->obi->mat, p[3]);
    }

    if(t == 0.0f) {
        copy_v3_v3(spoint->co, p[1]);
        spoint->strandco= sseg->v[1]->strandco;

        spoint->dtstrandco= (sseg->v[2]->strandco - sseg->v[0]->strandco);
        if(sseg->v[0] != sseg->v[1])
            spoint->dtstrandco *= 0.5f;
    }
    else if(t == 1.0f) {
        copy_v3_v3(spoint->co, p[2]);
        spoint->strandco= sseg->v[2]->strandco;

        spoint->dtstrandco= (sseg->v[3]->strandco - sseg->v[1]->strandco);
        if(sseg->v[3] != sseg->v[2])
            spoint->dtstrandco *= 0.5f;
    }
    else {
        key_curve_position_weights(t, data, type);
        spoint->co[0]= data[0]*p[0][0] + data[1]*p[1][0] + data[2]*p[2][0] + data[3]*p[3][0];
        spoint->co[1]= data[0]*p[0][1] + data[1]*p[1][1] + data[2]*p[2][1] + data[3]*p[3][1];
        spoint->co[2]= data[0]*p[0][2] + data[1]*p[1][2] + data[2]*p[2][2] + data[3]*p[3][2];
        spoint->strandco= (1.0f-t)*sseg->v[1]->strandco + t*sseg->v[2]->strandco;
    }

    key_curve_tangent_weights(t, data, type);
    spoint->dtco[0]= data[0]*p[0][0] + data[1]*p[1][0] + data[2]*p[2][0] + data[3]*p[3][0];
    spoint->dtco[1]= data[0]*p[0][1] + data[1]*p[1][1] + data[2]*p[2][1] + data[3]*p[3][1];
    spoint->dtco[2]= data[0]*p[0][2] + data[1]*p[1][2] + data[2]*p[2][2] + data[3]*p[3][2];

    normalize_v3_v3(spoint->tan, spoint->dtco);
    normalize_v3_v3(spoint->nor, spoint->co);
    negate_v3(spoint->nor);

    spoint->width= strand_eval_width(ma, spoint->strandco);
    
    /* simplification */
    simplify= RE_strandren_get_simplify(strandbuf->obr, sseg->strand, 0);
    spoint->alpha= (simplify)? simplify[1]: 1.0f;

    /* outer points */
    cross_v3_v3v3(cross, spoint->co, spoint->tan);

    w= spoint->co[2]*strandbuf->winmat[2][3] + strandbuf->winmat[3][3];
    dx= strandbuf->winx*cross[0]*strandbuf->winmat[0][0]/w;
    dy= strandbuf->winy*cross[1]*strandbuf->winmat[1][1]/w;
    w= sqrt(dx*dx + dy*dy);

    if(w > 0.0f) {
        if(strandbuf->flag & R_STRAND_B_UNITS) {
            const float crosslen= len_v3(cross);
            w= 2.0f*crosslen*strandbuf->minwidth/w;

            if(spoint->width < w) {
                spoint->alpha= spoint->width/w;
                spoint->width= w;
            }

            if(simplify)
                /* squared because we only change width, not length */
                spoint->width *= simplify[0]*simplify[0];

            mul_v3_fl(cross, spoint->width*0.5f/crosslen);
        }
        else
            mul_v3_fl(cross, spoint->width/w);
    }

    sub_v3_v3v3(spoint->co1, spoint->co, cross);
    add_v3_v3v3(spoint->co2, spoint->co, cross);

    copy_v3_v3(spoint->dsco, cross);
}

/* *************** */

static void interpolate_vec1(float *v1, float *v2, float t, float negt, float *v)
{
    v[0]= negt*v1[0] + t*v2[0];
}

static void interpolate_vec3(float *v1, float *v2, float t, float negt, float *v)
{
    v[0]= negt*v1[0] + t*v2[0];
    v[1]= negt*v1[1] + t*v2[1];
    v[2]= negt*v1[2] + t*v2[2];
}

static void interpolate_vec4(float *v1, float *v2, float t, float negt, float *v)
{
    v[0]= negt*v1[0] + t*v2[0];
    v[1]= negt*v1[1] + t*v2[1];
    v[2]= negt*v1[2] + t*v2[2];
    v[3]= negt*v1[3] + t*v2[3];
}

static void interpolate_shade_result(ShadeResult *shr1, ShadeResult *shr2, float t, ShadeResult *shr, int addpassflag)
{
    float negt= 1.0f - t;

    interpolate_vec4(shr1->combined, shr2->combined, t, negt, shr->combined);

    if(addpassflag & SCE_PASS_VECTOR) {
        interpolate_vec4(shr1->winspeed, shr2->winspeed, t, negt, shr->winspeed);
    }
    /* optim... */
    if(addpassflag & ~(SCE_PASS_VECTOR)) {
        if(addpassflag & SCE_PASS_Z)
            interpolate_vec1(&shr1->z, &shr2->z, t, negt, &shr->z);
        if(addpassflag & SCE_PASS_RGBA)
            interpolate_vec4(shr1->col, shr2->col, t, negt, shr->col);
        if(addpassflag & SCE_PASS_NORMAL) {
            interpolate_vec3(shr1->nor, shr2->nor, t, negt, shr->nor);
            normalize_v3(shr->nor);
        }
        if(addpassflag & SCE_PASS_EMIT)
            interpolate_vec3(shr1->emit, shr2->emit, t, negt, shr->emit);
        if(addpassflag & SCE_PASS_DIFFUSE)
            interpolate_vec3(shr1->diff, shr2->diff, t, negt, shr->diff);
        if(addpassflag & SCE_PASS_SPEC)
            interpolate_vec3(shr1->spec, shr2->spec, t, negt, shr->spec);
        if(addpassflag & SCE_PASS_SHADOW)
            interpolate_vec3(shr1->shad, shr2->shad, t, negt, shr->shad);
        if(addpassflag & SCE_PASS_AO)
            interpolate_vec3(shr1->ao, shr2->ao, t, negt, shr->ao);
        if(addpassflag & SCE_PASS_ENVIRONMENT)
            interpolate_vec3(shr1->env, shr2->env, t, negt, shr->env);
        if(addpassflag & SCE_PASS_INDIRECT)
            interpolate_vec3(shr1->indirect, shr2->indirect, t, negt, shr->indirect);
        if(addpassflag & SCE_PASS_REFLECT)
            interpolate_vec3(shr1->refl, shr2->refl, t, negt, shr->refl);
        if(addpassflag & SCE_PASS_REFRACT)
            interpolate_vec3(shr1->refr, shr2->refr, t, negt, shr->refr);
        if(addpassflag & SCE_PASS_MIST)
            interpolate_vec1(&shr1->mist, &shr2->mist, t, negt, &shr->mist);
    }
}

static void strand_apply_shaderesult_alpha(ShadeResult *shr, float alpha)
{
    if(alpha < 1.0f) {
        shr->combined[0] *= alpha;
        shr->combined[1] *= alpha;
        shr->combined[2] *= alpha;
        shr->combined[3] *= alpha;

        shr->col[0] *= alpha;
        shr->col[1] *= alpha;
        shr->col[2] *= alpha;
        shr->col[3] *= alpha;

        shr->alpha *= alpha;
    }
}

static void strand_shade_point(Render *re, ShadeSample *ssamp, StrandSegment *sseg, StrandVert *svert, StrandPoint *spoint)
{
    ShadeInput *shi= ssamp->shi;
    ShadeResult *shr= ssamp->shr;
    VlakRen vlr;
    int seed;

    memset(&vlr, 0, sizeof(vlr));
    vlr.flag= R_SMOOTH;
    if(sseg->buffer->ma->mode & MA_TANGENT_STR)
        vlr.flag |= R_TANGENT;

    shi->vlr= &vlr;
    shi->v1= NULL;
    shi->v2= NULL;
    shi->v3= NULL;
    shi->strand= sseg->strand;
    shi->obi= sseg->obi;
    shi->obr= sseg->obi->obr;

    /* cache for shadow */
    shi->samplenr= re->shadowsamplenr[shi->thread]++;

    /* all samples */
    shi->mask= 0xFFFF;

    /* seed RNG for consistent results across tiles */
    seed = shi->strand->index + (svert - shi->strand->vert);
    BLI_thread_srandom(shi->thread, seed);

    shade_input_set_strand(shi, sseg->strand, spoint);
    shade_input_set_strand_texco(shi, sseg->strand, sseg->v[1], spoint);
    
    /* init material vars */
    shade_input_init_material(shi);
    
    /* shade */
    shade_samples_do_AO(ssamp);
    shade_input_do_shade(shi, shr);

    /* apply simplification */
    strand_apply_shaderesult_alpha(shr, spoint->alpha);

    /* include lamphalos for strand, since halo layer was added already */
    if(re->flag & R_LAMPHALO)
        if(shi->layflag & SCE_LAY_HALO)
            renderspothalo(shi, shr->combined, shr->combined[3]);
    
    shi->strand= NULL;
}

/* *************** */

struct StrandShadeCache {
    GHash *resulthash;
    GHash *refcounthash;
    MemArena *memarena;
};

StrandShadeCache *strand_shade_cache_create(void)
{
    StrandShadeCache *cache;

    cache= MEM_callocN(sizeof(StrandShadeCache), "StrandShadeCache");
    cache->resulthash= BLI_ghash_new(BLI_ghashutil_ptrhash, BLI_ghashutil_ptrcmp, "strand_shade_cache_create1 gh");
    cache->refcounthash= BLI_ghash_new(BLI_ghashutil_ptrhash, BLI_ghashutil_ptrcmp, "strand_shade_cache_create2 gh");
    cache->memarena= BLI_memarena_new(BLI_MEMARENA_STD_BUFSIZE, "strand shade cache arena");
    
    return cache;
}

void strand_shade_cache_free(StrandShadeCache *cache)
{
    BLI_ghash_free(cache->refcounthash, NULL, NULL);
    BLI_ghash_free(cache->resulthash, NULL, (GHashValFreeFP)MEM_freeN);
    BLI_memarena_free(cache->memarena);
    MEM_freeN(cache);
}

static void strand_shade_get(Render *re, StrandShadeCache *cache, ShadeSample *ssamp, StrandSegment *sseg, StrandVert *svert)
{
    ShadeResult *hashshr;
    StrandPoint p;
    int *refcount;

    hashshr= BLI_ghash_lookup(cache->resulthash, svert);
    refcount= BLI_ghash_lookup(cache->refcounthash, svert);

    if(!hashshr) {
        /* not shaded yet, shade and insert into hash */
        p.t= (sseg->v[1] == svert)? 0.0f: 1.0f;
        strand_eval_point(sseg, &p);
        strand_shade_point(re, ssamp, sseg, svert, &p);

        hashshr= MEM_callocN(sizeof(ShadeResult), "HashShadeResult");
        *hashshr= ssamp->shr[0];
        BLI_ghash_insert(cache->resulthash, svert, hashshr);
    }
    else
        /* already shaded, just copy previous result from hash */
        ssamp->shr[0]= *hashshr;
    
    /* lower reference count and remove if not needed anymore by any samples */
    (*refcount)--;
    if(*refcount == 0) {
        BLI_ghash_remove(cache->resulthash, svert, NULL, (GHashValFreeFP)MEM_freeN);
        BLI_ghash_remove(cache->refcounthash, svert, NULL, NULL);
    }
}

void strand_shade_segment(Render *re, StrandShadeCache *cache, StrandSegment *sseg, ShadeSample *ssamp, float t, float s, int addpassflag)
{
    ShadeResult shr1, shr2;

    /* get shading for two endpoints and interpolate */
    strand_shade_get(re, cache, ssamp, sseg, sseg->v[1]);
    shr1= ssamp->shr[0];
    strand_shade_get(re, cache, ssamp, sseg, sseg->v[2]);
    shr2= ssamp->shr[0];

    interpolate_shade_result(&shr1, &shr2, t, ssamp->shr, addpassflag);

    /* apply alpha along width */
    if(sseg->buffer->widthfade != 0.0f) {
        s = 1.0f - pow(fabs(s), sseg->buffer->widthfade);

        strand_apply_shaderesult_alpha(ssamp->shr, s);
    }
}

void strand_shade_unref(StrandShadeCache *cache, StrandVert *svert)
{
    int *refcount;

    /* lower reference count and remove if not needed anymore by any samples */
    refcount= BLI_ghash_lookup(cache->refcounthash, svert);

    (*refcount)--;
    if(*refcount == 0) {
        BLI_ghash_remove(cache->resulthash, svert, NULL, (GHashValFreeFP)MEM_freeN);
        BLI_ghash_remove(cache->refcounthash, svert, NULL, NULL);
    }
}

static void strand_shade_refcount(StrandShadeCache *cache, StrandVert *svert)
{
    int *refcount= BLI_ghash_lookup(cache->refcounthash, svert);

    if(!refcount) {
        refcount= BLI_memarena_alloc(cache->memarena, sizeof(int));
        *refcount= 1;
        BLI_ghash_insert(cache->refcounthash, svert, refcount);
    }
    else
        (*refcount)++;
}

/* *************** */

typedef struct StrandPart {
    Render *re;
    ZSpan *zspan;

    APixstrand *apixbuf;
    int *totapixbuf;
    int *rectz;
    int *rectmask;
    intptr_t *rectdaps;
    int rectx, recty;
    int sample;
    int shadow;
    float (*jit)[2];

    StrandSegment *segment;
    float t[3], s[3];

    StrandShadeCache *cache;
} StrandPart;

typedef struct StrandSortSegment {
    struct StrandSortSegment *next;
    int obi, strand, segment;
    float z;
} StrandSortSegment;

static int compare_strand_segment(const void *poin1, const void *poin2)
{
    const StrandSortSegment *seg1= (const StrandSortSegment*)poin1;
    const StrandSortSegment *seg2= (const StrandSortSegment*)poin2;

    if(seg1->z < seg2->z)
        return -1;
    else if(seg1->z == seg2->z)
        return 0;
    else
        return 1;
}

static void do_strand_point_project(float winmat[][4], ZSpan *zspan, float *co, float *hoco, float *zco)
{
    projectvert(co, winmat, hoco);
    hoco_to_zco(zspan, zco, hoco);
}

static void strand_project_point(float winmat[][4], float winx, float winy, StrandPoint *spoint)
{
    float div;

    projectvert(spoint->co, winmat, spoint->hoco);

    div= 1.0f/spoint->hoco[3];
    spoint->x= spoint->hoco[0]*div*winx*0.5f;
    spoint->y= spoint->hoco[1]*div*winy*0.5f;
}

static APixstrand *addpsmainAstrand(ListBase *lb)
{
    APixstrMain *psm;

    psm= MEM_mallocN(sizeof(APixstrMain), "addpsmainA");
    BLI_addtail(lb, psm);
    psm->ps= MEM_callocN(4096*sizeof(APixstrand),"pixstr");

    return psm->ps;
}

static APixstrand *addpsAstrand(ZSpan *zspan)
{
    /* make new PS */
    if(zspan->apstrandmcounter==0) {
        zspan->curpstrand= addpsmainAstrand(zspan->apsmbase);
        zspan->apstrandmcounter= 4095;
    }
    else {
        zspan->curpstrand++;
        zspan->apstrandmcounter--;
    }
    return zspan->curpstrand;
}

#define MAX_ZROW    2000

static void do_strand_fillac(void *handle, int x, int y, float u, float v, float z)
{
    StrandPart *spart= (StrandPart*)handle;
    StrandShadeCache *cache= spart->cache;
    StrandSegment *sseg= spart->segment;
    APixstrand *apn, *apnew;
    float t, s;
    int offset, mask, obi, strnr, seg, zverg, bufferz, maskz=0;

    offset = y*spart->rectx + x;
    obi= sseg->obi - spart->re->objectinstance;
    strnr= sseg->strand->index + 1;
    seg= sseg->v[1] - sseg->strand->vert;
    mask= (1<<spart->sample);

    /* check against solid z-buffer */
    zverg= (int)z;

    if(spart->rectdaps) {
        /* find the z of the sample */
        PixStr *ps;
        intptr_t *rd= spart->rectdaps + offset;
        
        bufferz= 0x7FFFFFFF;
        if(spart->rectmask) maskz= 0x7FFFFFFF;
        
        if(*rd) {   
            for(ps= (PixStr *)(*rd); ps; ps= ps->next) {
                if(mask & ps->mask) {
                    bufferz= ps->z;
                    if(spart->rectmask)
                        maskz= ps->maskz;
                    break;
                }
            }
        }
    }
    else {
        bufferz= (spart->rectz)? spart->rectz[offset]: 0x7FFFFFFF;
        if(spart->rectmask)
            maskz= spart->rectmask[offset];
    }

#define CHECK_ADD(n) \
    if(apn->p[n]==strnr && apn->obi[n]==obi && apn->seg[n]==seg) \
    { if(!(apn->mask[n] & mask)) { apn->mask[n] |= mask; apn->v[n] += t; apn->u[n] += s; } break; }
#define CHECK_ASSIGN(n) \
    if(apn->p[n]==0) \
    {apn->obi[n]= obi; apn->p[n]= strnr; apn->z[n]= zverg; apn->mask[n]= mask; apn->v[n]= t; apn->u[n]= s; apn->seg[n]= seg; break; }

    /* add to pixel list */
    if(zverg < bufferz && (spart->totapixbuf[offset] < MAX_ZROW)) {
        if(!spart->rectmask || zverg > maskz) {
            t = u*spart->t[0] + v*spart->t[1] + (1.0f-u-v)*spart->t[2];
            s = fabs(u*spart->s[0] + v*spart->s[1] + (1.0f-u-v)*spart->s[2]);

            apn= spart->apixbuf + offset;
            while(apn) {
                CHECK_ADD(0);
                CHECK_ADD(1);
                CHECK_ADD(2);
                CHECK_ADD(3);
                CHECK_ASSIGN(0);
                CHECK_ASSIGN(1);
                CHECK_ASSIGN(2);
                CHECK_ASSIGN(3);

                apnew= addpsAstrand(spart->zspan);
                SWAP(APixstrand, *apnew, *apn);
                apn->next= apnew;
                CHECK_ASSIGN(0);
            }

            if(cache) {
                strand_shade_refcount(cache, sseg->v[1]);
                strand_shade_refcount(cache, sseg->v[2]);
            }
            spart->totapixbuf[offset]++;
        }
    }
}

/* width is calculated in hoco space, to ensure strands are visible */
static int strand_test_clip(float winmat[][4], ZSpan *UNUSED(zspan), float *bounds, float *co, float *zcomp, float widthx, float widthy)
{
    float hoco[4];
    int clipflag= 0;

    projectvert(co, winmat, hoco);

    /* we compare z without perspective division for segment sorting */
    *zcomp= hoco[2];

    if(hoco[0]+widthx < bounds[0]*hoco[3]) clipflag |= 1;
    else if(hoco[0]-widthx > bounds[1]*hoco[3]) clipflag |= 2;
    
    if(hoco[1]-widthy > bounds[3]*hoco[3]) clipflag |= 4;
    else if(hoco[1]+widthy < bounds[2]*hoco[3]) clipflag |= 8;

    clipflag |= testclip(hoco);

    return clipflag;
}

static void do_scanconvert_strand(Render *UNUSED(re), StrandPart *spart, ZSpan *zspan, float t, float dt, float *co1, float *co2, float *co3, float *co4, int sample)
{
    float jco1[3], jco2[3], jco3[3], jco4[3], jx, jy;

    copy_v3_v3(jco1, co1);
    copy_v3_v3(jco2, co2);
    copy_v3_v3(jco3, co3);
    copy_v3_v3(jco4, co4);

    if(spart->jit) {
        jx= -spart->jit[sample][0];
        jy= -spart->jit[sample][1];

        jco1[0] += jx; jco1[1] += jy;
        jco2[0] += jx; jco2[1] += jy;
        jco3[0] += jx; jco3[1] += jy;
        jco4[0] += jx; jco4[1] += jy;

        /* XXX mblur? */
    }

    spart->sample= sample;

    spart->t[0]= t-dt;
    spart->s[0]= -1.0f;
    spart->t[1]= t-dt;
    spart->s[1]= 1.0f;
    spart->t[2]= t;
    spart->s[2]= 1.0f;
    zspan_scanconvert_strand(zspan, spart, jco1, jco2, jco3, do_strand_fillac);
    spart->t[0]= t-dt;
    spart->s[0]= -1.0f;
    spart->t[1]= t;
    spart->s[1]= 1.0f;
    spart->t[2]= t;
    spart->s[2]= -1.0f;
    zspan_scanconvert_strand(zspan, spart, jco1, jco3, jco4, do_strand_fillac);
}

static void strand_render(Render *re, StrandSegment *sseg, float winmat[][4], StrandPart *spart, ZSpan *zspan, int totzspan, StrandPoint *p1, StrandPoint *p2)
{
    if(spart) {
        float t= p2->t;
        float dt= p2->t - p1->t;
        int a;

        if(re->osa) {
            for(a=0; a<re->osa; a++)
                do_scanconvert_strand(re, spart, zspan, t, dt, p1->zco2, p1->zco1, p2->zco1, p2->zco2, a);
        }
        else
            do_scanconvert_strand(re, spart, zspan, t, dt, p1->zco2, p1->zco1, p2->zco1, p2->zco2, 0);
    }
    else {
        float hoco1[4], hoco2[4];
        int a, obi, index;
  
        obi= sseg->obi - re->objectinstance;
        index= sseg->strand->index;

        projectvert(p1->co, winmat, hoco1);
        projectvert(p2->co, winmat, hoco2);

  
        for(a=0; a<totzspan; a++) {
#if 0
            /* render both strand and single pixel wire to counter aliasing */
            zbufclip4(re, &zspan[a], obi, index, p1->hoco2, p1->hoco1, p2->hoco1, p2->hoco2, p1->clip2, p1->clip1, p2->clip1, p2->clip2);
#endif
            /* only render a line for now, which makes the shadow map more
               similiar across frames, and so reduces flicker */
            zbufsinglewire(&zspan[a], obi, index, hoco1, hoco2);
        }
    }
}

static int strand_segment_recursive(Render *re, float winmat[][4], StrandPart *spart, ZSpan *zspan, int totzspan, StrandSegment *sseg, StrandPoint *p1, StrandPoint *p2, int depth)
{
    StrandPoint p;
    StrandBuffer *buffer= sseg->buffer;
    float dot, d1[2], d2[2], len1, len2;

    if(depth == buffer->maxdepth)
        return 0;

    p.t= (p1->t + p2->t)*0.5f;
    strand_eval_point(sseg, &p);
    strand_project_point(buffer->winmat, buffer->winx, buffer->winy, &p);

    d1[0]= (p.x - p1->x);
    d1[1]= (p.y - p1->y);
    len1= d1[0]*d1[0] + d1[1]*d1[1];

    d2[0]= (p2->x - p.x);
    d2[1]= (p2->y - p.y);
    len2= d2[0]*d2[0] + d2[1]*d2[1];

    if(len1 == 0.0f || len2 == 0.0f)
        return 0;
    
    dot= d1[0]*d2[0] + d1[1]*d2[1];
    if(dot*dot > sseg->sqadaptcos*len1*len2)
        return 0;

    if(spart) {
        do_strand_point_project(winmat, zspan, p.co1, p.hoco1, p.zco1);
        do_strand_point_project(winmat, zspan, p.co2, p.hoco2, p.zco2);
    }
    else {
#if 0
        projectvert(p.co1, winmat, p.hoco1);
        projectvert(p.co2, winmat, p.hoco2);
        p.clip1= testclip(p.hoco1);
        p.clip2= testclip(p.hoco2);
#endif
    }

    if(!strand_segment_recursive(re, winmat, spart, zspan, totzspan, sseg, p1, &p, depth+1))
        strand_render(re, sseg, winmat, spart, zspan, totzspan, p1, &p);
    if(!strand_segment_recursive(re, winmat, spart, zspan, totzspan, sseg, &p, p2, depth+1))
        strand_render(re, sseg, winmat, spart, zspan, totzspan, &p, p2);
    
    return 1;
}

void render_strand_segment(Render *re, float winmat[][4], StrandPart *spart, ZSpan *zspan, int totzspan, StrandSegment *sseg)
{
    StrandBuffer *buffer= sseg->buffer;
    StrandPoint *p1= &sseg->point1;
    StrandPoint *p2= &sseg->point2;

    p1->t= 0.0f;
    p2->t= 1.0f;

    strand_eval_point(sseg, p1);
    strand_project_point(buffer->winmat, buffer->winx, buffer->winy, p1);
    strand_eval_point(sseg, p2);
    strand_project_point(buffer->winmat, buffer->winx, buffer->winy, p2);

    if(spart) {
        do_strand_point_project(winmat, zspan, p1->co1, p1->hoco1, p1->zco1);
        do_strand_point_project(winmat, zspan, p1->co2, p1->hoco2, p1->zco2);
        do_strand_point_project(winmat, zspan, p2->co1, p2->hoco1, p2->zco1);
        do_strand_point_project(winmat, zspan, p2->co2, p2->hoco2, p2->zco2);
    }
    else {
#if 0
        projectvert(p1->co1, winmat, p1->hoco1);
        projectvert(p1->co2, winmat, p1->hoco2);
        projectvert(p2->co1, winmat, p2->hoco1);
        projectvert(p2->co2, winmat, p2->hoco2);
        p1->clip1= testclip(p1->hoco1);
        p1->clip2= testclip(p1->hoco2);
        p2->clip1= testclip(p2->hoco1);
        p2->clip2= testclip(p2->hoco2);
#endif
    }

    if(!strand_segment_recursive(re, winmat, spart, zspan, totzspan, sseg, p1, p2, 0))
        strand_render(re, sseg, winmat, spart, zspan, totzspan, p1, p2);
}

/* render call to fill in strands */
int zbuffer_strands_abuf(Render *re, RenderPart *pa, APixstrand *apixbuf, ListBase *apsmbase, unsigned int lay, int UNUSED(negzmask), float winmat[][4], int winx, int winy, int UNUSED(sample), float (*jit)[2], float clipcrop, int shadow, StrandShadeCache *cache)
{
    ObjectRen *obr;
    ObjectInstanceRen *obi;
    ZSpan zspan;
    StrandRen *strand=0;
    StrandVert *svert;
    StrandBound *sbound;
    StrandPart spart;
    StrandSegment sseg;
    StrandSortSegment *sortsegments = NULL, *sortseg, *firstseg;
    MemArena *memarena;
    float z[4], bounds[4], obwinmat[4][4];
    int a, b, c, i, totsegment, clip[4];

    if(re->test_break(re->tbh))
        return 0;
    if(re->totstrand == 0)
        return 0;

    /* setup StrandPart */
    memset(&spart, 0, sizeof(spart));

    spart.re= re;
    spart.rectx= pa->rectx;
    spart.recty= pa->recty;
    spart.apixbuf= apixbuf;
    spart.zspan= &zspan;
    spart.rectdaps= pa->rectdaps;
    spart.rectz= pa->rectz;
    spart.rectmask= pa->rectmask;
    spart.cache= cache;
    spart.shadow= shadow;
    spart.jit= jit;

    zbuf_alloc_span(&zspan, pa->rectx, pa->recty, clipcrop);

    /* needed for transform from hoco to zbuffer co */
    zspan.zmulx= ((float)winx)/2.0f;
    zspan.zmuly= ((float)winy)/2.0f;
    
    zspan.zofsx= -pa->disprect.xmin;
    zspan.zofsy= -pa->disprect.ymin;

    /* to center the sample position */
    if(!shadow) {
        zspan.zofsx -= 0.5f;
        zspan.zofsy -= 0.5f;
    }

    zspan.apsmbase= apsmbase;

    /* clipping setup */
    bounds[0]= (2*pa->disprect.xmin - winx-1)/(float)winx;
    bounds[1]= (2*pa->disprect.xmax - winx+1)/(float)winx;
    bounds[2]= (2*pa->disprect.ymin - winy-1)/(float)winy;
    bounds[3]= (2*pa->disprect.ymax - winy+1)/(float)winy;

    memarena= BLI_memarena_new(BLI_MEMARENA_STD_BUFSIZE, "strand sort arena");
    firstseg= NULL;
    totsegment= 0;

    /* for all object instances */
    for(obi=re->instancetable.first, i=0; obi; obi=obi->next, i++) {
        Material *ma;
        float widthx, widthy;

        obr= obi->obr;

        if(!obr->strandbuf || !(obr->strandbuf->lay & lay))
            continue;

        /* compute matrix and try clipping whole object */
        if(obi->flag & R_TRANSFORMED)
            mult_m4_m4m4(obwinmat, winmat, obi->mat);
        else
            copy_m4_m4(obwinmat, winmat);

        /* test if we should skip it */
        ma = obr->strandbuf->ma;

        if(shadow && !(ma->mode & MA_SHADBUF))
            continue;
        else if(!shadow && (ma->mode & MA_ONLYCAST))
            continue;

        if(clip_render_object(obi->obr->boundbox, bounds, obwinmat))
            continue;
        
        widthx= obr->strandbuf->maxwidth*obwinmat[0][0];
        widthy= obr->strandbuf->maxwidth*obwinmat[1][1];

        /* for each bounding box containing a number of strands */
        sbound= obr->strandbuf->bound;
        for(c=0; c<obr->strandbuf->totbound; c++, sbound++) {
            if(clip_render_object(sbound->boundbox, bounds, obwinmat))
                continue;

            /* for each strand in this bounding box */
            for(a=sbound->start; a<sbound->end; a++) {
                strand= RE_findOrAddStrand(obr, a);
                svert= strand->vert;

                /* keep clipping and z depth for 4 control points */
                clip[1]= strand_test_clip(obwinmat, &zspan, bounds, svert->co, &z[1], widthx, widthy);
                clip[2]= strand_test_clip(obwinmat, &zspan, bounds, (svert+1)->co, &z[2], widthx, widthy);
                clip[0]= clip[1]; z[0]= z[1];

                for(b=0; b<strand->totvert-1; b++, svert++) {
                    /* compute 4th point clipping and z depth */
                    if(b < strand->totvert-2) {
                        clip[3]= strand_test_clip(obwinmat, &zspan, bounds, (svert+2)->co, &z[3], widthx, widthy);
                    }
                    else {
                        clip[3]= clip[2]; z[3]= z[2];
                    }

                    /* check clipping and add to sortsegments buffer */
                    if(!(clip[0] & clip[1] & clip[2] & clip[3])) {
                        sortseg= BLI_memarena_alloc(memarena, sizeof(StrandSortSegment));
                        sortseg->obi= i;
                        sortseg->strand= strand->index;
                        sortseg->segment= b;

                        sortseg->z= 0.5f*(z[1] + z[2]);

                        sortseg->next= firstseg;
                        firstseg= sortseg;
                        totsegment++;
                    }

                    /* shift clipping and z depth */
                    clip[0]= clip[1]; z[0]= z[1];
                    clip[1]= clip[2]; z[1]= z[2];
                    clip[2]= clip[3]; z[2]= z[3];
                }
            }
        }
    }

    if(!re->test_break(re->tbh)) {
        /* convert list to array and sort */
        sortsegments= MEM_mallocN(sizeof(StrandSortSegment)*totsegment, "StrandSortSegment");
        for(a=0, sortseg=firstseg; a<totsegment; a++, sortseg=sortseg->next)
            sortsegments[a]= *sortseg;
        qsort(sortsegments, totsegment, sizeof(StrandSortSegment), compare_strand_segment);
    }

    BLI_memarena_free(memarena);

    spart.totapixbuf= MEM_callocN(sizeof(int)*pa->rectx*pa->recty, "totapixbuf");

    if(!re->test_break(re->tbh)) {
        /* render segments in sorted order */
        sortseg= sortsegments;
        for(a=0; a<totsegment; a++, sortseg++) {
            if(re->test_break(re->tbh))
                break;

            obi= &re->objectinstance[sortseg->obi];
            obr= obi->obr;

            sseg.obi= obi;
            sseg.strand= RE_findOrAddStrand(obr, sortseg->strand);
            sseg.buffer= sseg.strand->buffer;
            sseg.sqadaptcos= sseg.buffer->adaptcos;
            sseg.sqadaptcos *= sseg.sqadaptcos;

            svert= sseg.strand->vert + sortseg->segment;
            sseg.v[0]= (sortseg->segment > 0)? (svert-1): svert;
            sseg.v[1]= svert;
            sseg.v[2]= svert+1;
            sseg.v[3]= (sortseg->segment < sseg.strand->totvert-2)? svert+2: svert+1;
            sseg.shaded= 0;

            spart.segment= &sseg;

            render_strand_segment(re, winmat, &spart, &zspan, 1, &sseg);
        }
    }

    if(sortsegments)
        MEM_freeN(sortsegments);
    MEM_freeN(spart.totapixbuf);
    
    zbuf_free_span(&zspan);

    return totsegment;
}

/* *************** */

StrandSurface *cache_strand_surface(Render *re, ObjectRen *obr, DerivedMesh *dm, float mat[][4], int timeoffset)
{
    StrandSurface *mesh;
    MFace *mface;
    MVert *mvert;
    float (*co)[3];
    int a, totvert, totface;

    totvert= dm->getNumVerts(dm);
    totface= dm->getNumFaces(dm);

    for(mesh=re->strandsurface.first; mesh; mesh=mesh->next)
        if(mesh->obr.ob == obr->ob && mesh->obr.par == obr->par
            && mesh->obr.index == obr->index && mesh->totvert==totvert && mesh->totface==totface)
            break;

    if(!mesh) {
        mesh= MEM_callocN(sizeof(StrandSurface), "StrandSurface");
        mesh->obr= *obr;
        mesh->totvert= totvert;
        mesh->totface= totface;
        mesh->face= MEM_callocN(sizeof(int)*4*mesh->totface, "StrandSurfFaces");
        mesh->ao= MEM_callocN(sizeof(float)*3*mesh->totvert, "StrandSurfAO");
        mesh->env= MEM_callocN(sizeof(float)*3*mesh->totvert, "StrandSurfEnv");
        mesh->indirect= MEM_callocN(sizeof(float)*3*mesh->totvert, "StrandSurfIndirect");
        BLI_addtail(&re->strandsurface, mesh);
    }

    if(timeoffset == -1 && !mesh->prevco)
        mesh->prevco= co= MEM_callocN(sizeof(float)*3*mesh->totvert, "StrandSurfCo");
    else if(timeoffset == 0 && !mesh->co)
        mesh->co= co= MEM_callocN(sizeof(float)*3*mesh->totvert, "StrandSurfCo");
    else if(timeoffset == 1 && !mesh->nextco)
        mesh->nextco= co= MEM_callocN(sizeof(float)*3*mesh->totvert, "StrandSurfCo");
    else
        return mesh;

    mvert= dm->getVertArray(dm);
    for(a=0; a<mesh->totvert; a++, mvert++) {
        copy_v3_v3(co[a], mvert->co);
        mul_m4_v3(mat, co[a]);
    }

    mface= dm->getFaceArray(dm);
    for(a=0; a<mesh->totface; a++, mface++) {
        mesh->face[a][0]= mface->v1;
        mesh->face[a][1]= mface->v2;
        mesh->face[a][2]= mface->v3;
        mesh->face[a][3]= mface->v4;
    }

    return mesh;
}

void free_strand_surface(Render *re)
{
    StrandSurface *mesh;

    for(mesh=re->strandsurface.first; mesh; mesh=mesh->next) {
        if(mesh->co) MEM_freeN(mesh->co);
        if(mesh->prevco) MEM_freeN(mesh->prevco);
        if(mesh->nextco) MEM_freeN(mesh->nextco);
        if(mesh->ao) MEM_freeN(mesh->ao);
        if(mesh->env) MEM_freeN(mesh->env);
        if(mesh->indirect) MEM_freeN(mesh->indirect);
        if(mesh->face) MEM_freeN(mesh->face);
    }

    BLI_freelistN(&re->strandsurface);
}

void strand_minmax(StrandRen *strand, float *min, float *max, float width)
{
    StrandVert *svert;
    float vec[3], width2= 2.0f*width;
    int a;

    for(a=0, svert=strand->vert; a<strand->totvert; a++, svert++) {
        copy_v3_v3(vec, svert->co);
        DO_MINMAX(vec, min, max);
        
        if(width!=0.0f) {
            vec[0]+= width; vec[1]+= width; vec[2]+= width;
            DO_MINMAX(vec, min, max);
            vec[0]-= width2; vec[1]-= width2; vec[2]-= width2;
            DO_MINMAX(vec, min, max);
        }
    }
}