RAS_texmatrix.cpp

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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: all of this file.
 *
 * Contributor(s): none yet.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include "RAS_TexMatrix.h"

void RAS_CalcTexMatrix(RAS_TexVert p[3],MT_Point3& origin,MT_Vector3& udir,MT_Vector3& vdir)
{
// precondition: 3 vertices are non-colinear

    MT_Vector3 vec1 = p[1].xyz()-p[0].xyz();
    MT_Vector3 vec2 = p[2].xyz()-p[0].xyz();
    MT_Vector3 normal = vec1.cross(vec2);
    normal.normalize();

    // determine which coordinate we drop, ie. max coordinate in the normal
    

    int ZCOORD = normal.closestAxis();
    int XCOORD = (ZCOORD+1)%3;
    int YCOORD = (ZCOORD+2)%3;
        
    // ax+by+cz+d=0
    MT_Scalar d = -p[0].xyz().dot(normal);
    

    MT_Matrix3x3 mat3(  p[0].getUV1()[0],p[0].getUV1()[1],  1,
                        p[1].getUV1()[0],p[1].getUV1()[1],  1,
                        p[2].getUV1()[0],p[2].getUV1()[1],  1);


    MT_Matrix3x3 mat3inv = mat3.inverse();

    MT_Vector3 p123x(p[0].xyz()[XCOORD],p[1].xyz()[XCOORD],p[2].xyz()[XCOORD]);
    MT_Vector3 resultx = mat3inv*p123x;
    MT_Vector3 p123y(p[0].xyz()[YCOORD],p[1].xyz()[YCOORD],p[2].xyz()[YCOORD]);
    MT_Vector3 resulty = mat3inv*p123y;

    // normal[ZCOORD] is not zero, because it's chosen to be maximal (absolute), and normal has length 1, 
    // so at least on of the coords is <> 0

    //droppedvalue udir.dot(normal) =0
    MT_Scalar droppedu = -(resultx.x()*normal[XCOORD]+resulty.x()*normal[YCOORD])/normal[ZCOORD];
    udir[XCOORD] = resultx.x();
    udir[YCOORD] = resulty.x();
    udir[ZCOORD] = droppedu;
    MT_Scalar droppedv = -(resultx.y()*normal[XCOORD]+resulty.y()*normal[YCOORD])/normal[ZCOORD];
    vdir[XCOORD] = resultx.y();
    vdir[YCOORD] = resulty.y();
    vdir[ZCOORD] = droppedv;
    // droppedvalue b = -(ax+cz+d)/y;
    MT_Scalar droppedvalue = -((resultx.z()*normal[XCOORD] + resulty.z()*normal[YCOORD]+d))/normal[ZCOORD];
    origin[XCOORD] = resultx.z();
    origin[YCOORD] = resulty.z();
    origin[ZCOORD] = droppedvalue;
    

}

#ifdef _TEXOWNMAIN

int main()
{

    MT_Point2 puv0={0,0};
    MT_Point3 pxyz0 (0,0,128);

    MT_Scalar puv1[2]={1,0};
    MT_Point3 pxyz1(128,0,128);

    MT_Scalar puv2[2]={1,1};
    MT_Point3 pxyz2(128,0,0);

    RAS_TexVert p0(pxyz0,puv0);
    RAS_TexVert p1(pxyz1,puv1);
    RAS_TexVert p2(pxyz2,puv2);

    RAS_TexVert vertices[3] = 
    {
        p0,
        p1,
        p2
    };

    MT_Vector3 udir,vdir;
    MT_Point3 origin;
    CalcTexMatrix(vertices,origin,udir,vdir);

    MT_Point3 testpoint(128,32,64);

    MT_Scalar lenu = udir.length2();
    MT_Scalar lenv = vdir.length2();

    MT_Scalar testu=((pxyz2-origin).dot(udir))/lenu;
    MT_Scalar testv=((pxyz2-origin).dot(vdir))/lenv;




    return 0;
}

#endif // _TEXOWNMAIN