void TriangleMesh::PostIntersect(Intersection &isect) const {
const Triangle &tri = m_Triangles[isect.primID];
Normal &Ng = isect.Ng;
float u = isect.uv[0], v = isect.uv[1], w = 1.0f-u-v;
Point2 st0, st1, st2;
if(m_STs.size() == 0) {
st0 = Point2(0.f, 0.f);
st1 = Point2(1.f, 0.f);
st2 = Point2(0.f, 1.f);
isect.st = isect.uv;
} else {
st0 = m_STs[tri.idx[0]];
st1 = m_STs[tri.idx[1]];
st2 = m_STs[tri.idx[2]];
isect.st = w*st0 + u*st1 + v*st2;
}
if(m_Normals.size() == 0) {
isect.Ns = Ng;
} else {
const Normal &n0 = m_Normals[tri.idx[0]];
const Normal &n1 = m_Normals[tri.idx[1]];
const Normal &n2 = m_Normals[tri.idx[2]];
//Vector dPdu = p1 - p0, dPdv = p2 - p2;
Normal Ns = w*n0 + u*n1 + v*n2;
float sqLen = Ns.squaredNorm();
//Ns = sqLen > 0.f ? Ns*Rsqrt(sqLen) : isect.Ng;
if(sqLen > 0.f)
Ns *= Rsqrt(sqLen);
else
Ns = isect.Ng;
if (Ns.dot(Ng) < 0.f)
Ns = -Ns;
isect.Ns = Ns;
}
if(Ng.squaredNorm() <= 0.f) {
// Degenerated triangle
isect.dPds = Vector(0.f);
isect.dPdt = Vector(0.f);
} else {
const PointA &p0 = m_Vertices[tri.idx[0]];
const PointA &p1 = m_Vertices[tri.idx[1]];
const PointA &p2 = m_Vertices[tri.idx[2]];
Vector dP1 = p1 - p0, dP2 = p2 - p0;
Vector2 dST1 = st1 - st0, dST2 = st2 - st0;
float determinant = dST1[0] * dST2[1] - dST1[1] * dST2[0];
if(determinant == 0.f) {
// Degenerated st
CoordinateSystem(Ng, isect.dPds, isect.dPdt);
} else {
float invDet = Rcp(determinant);
isect.dPds = ( dST2[1] * dP1 - dST1[1] * dP2)*invDet;
isect.dPdt = (-dST2[0] * dP1 + dST1[0] * dP2)*invDet;
}
}
}
//----------------------------------------------------------------------------------
//
//----------------------------------------------------------------------------------
void Vector3D::Normal( Vector3D& o, const Vector3D& in )
{
float inv = Rsqrt( in.X * in.X + in.Y * in.Y + in.Z * in.Z );
o.X = in.X * inv;
o.Y = in.Y * inv;
o.Z = in.Z * inv;
}
