static void __gluMultMatrixVecd(const GLdouble matrix[16], const GLdouble in[4],
		      GLdouble out[4])
{
    int i;

    for (i=0; i<4; i++) {
	out[i] = 
	    in[0] * matrix[0*4+i] +
	    in[1] * matrix[1*4+i] +
	    in[2] * matrix[2*4+i] +
	    in[3] * matrix[3*4+i];
    }
}

GLint GLAPIENTRY
gluProject(GLdouble objx, GLdouble objy, GLdouble objz, 
	      const GLdouble modelMatrix[16], 
	      const GLdouble projMatrix[16],
              const GLint viewport[4],
	      GLdouble *winx, GLdouble *winy, GLdouble *winz)
{
    double in[4];
    double out[4];

    in[0]=objx;
    in[1]=objy;
    in[2]=objz;
    in[3]=1.0;
    __gluMultMatrixVecd(modelMatrix, in, out);
    __gluMultMatrixVecd(projMatrix, out, in);
    if (in[3] == 0.0) return(GL_FALSE);
    in[0] /= in[3];
    in[1] /= in[3];
    in[2] /= in[3];
    /* Map x, y and z to range 0-1 */
    in[0] = in[0] * 0.5 + 0.5;
    in[1] = in[1] * 0.5 + 0.5;
    in[2] = in[2] * 0.5 + 0.5;

    /* Map x,y to viewport */
    in[0] = in[0] * viewport[2] + viewport[0];
    in[1] = in[1] * viewport[3] + viewport[1];

    *winx=in[0];
    *winy=in[1];
    *winz=in[2];
    return(GL_TRUE);
}

3D to 2D coordinates

textmate

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