Triangle.cc

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#include <esg/geometry/Triangle.h>

using namespace esg;

// ---- public ---

Geometry* Triangle::clone(const Matrix4* pTrMat) const
{
    Triangle* pRet = new Triangle;
    pRet->_duplicate_attributes(*this);
    if (pTrMat) pRet->_transform(*pTrMat);
    return pRet;
}

void Triangle::randomSample(int mask, PointEnv& pe, double* pdf)
{
    
    /*
     * Reference: 
     *    Arvo J. et al., State of the Art in Monte Carlo Ray Tracing 
     *    for Relistic Image Sythesis, 
     *    SIGGRAPH2001 Course 29, Aug 13, 2001. Page 25.
     */

    pe.mask = ENV_HAVE_NOTHING;
    if (!(mask & ENV_WANT_SURFACE_POINT|ENV_WANT_UV_COORD|ENV_WANT_NORMAL))
        return;
        
    Vector3 u(_get_vertex(1));
    Vector3 v(_get_vertex(2));
    pe.intersection.set(_get_vertex(0));
    u.sub(pe.intersection);
    v.sub(pe.intersection);
    double s = 1 - sqrt(1 - ESG_DBL_RAND);
    u.scale(s);
    v.scale((1 - s) * ESG_DBL_RAND);
    pe.intersection.add(u);
    pe.intersection.add(v);
    
    // get UV coord or interpolate normal - unefficient !
    Vector3* n =(((mask&ENV_WANT_NORMAL)  &&_normals)  ? &(pe.normal) : NULL);
    Vector2* uv=(((mask&ENV_WANT_UV_COORD)&&_uvCoords) ? &(pe.uvCoord) : NULL);
    if (n || uv) {
        (void) _point_inside_polygon(pe.intersection, n, uv);
        if (n) {
            pe.normalOrientation = PointEnv::OUTWARDS_NORMAL;
            pe.mask |= ENV_HAVE_NORMAL;
        } else {
            if (mask & ENV_WANT_NORMAL) {
                // intersection is found but the normal vector
                // cannot be interpolated  => set it to the facet normal
                pe.normal.set(_normal);
                if (_normalFixed) pe.normalOrientation = PointEnv::OUTWARDS_NORMAL;
                else              pe.normalOrientation = PointEnv::RANDOM_NORMAL;
                pe.mask |= ENV_HAVE_NORMAL;
            }
        }
    
        pe.mask |= ((uv) ?
                    ENV_HAVE_INTERFERENCE|ENV_HAVE_INTERSECTION|ENV_HAVE_UV_COORD :
                    ENV_HAVE_INTERFERENCE|ENV_HAVE_INTERSECTION);
    }

    if (pdf) *pdf = 1./_area;
}

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