int intersect3D_RayTriangle( Ray R, Triangle T, Point &I )
{
// Vector u, v, n; // triangle vectors
//Vector dir, w0, w; // ray vectors
float r, a, b; // params to calc ray-plane intersect
// get triangle edge vectors and plane normal
Vector u(T.V0(), T.V1());
Vector v(T.V0(), T.V2());
Vector n(u,v); // cross product
if (n.vecteurNull()) // triangle is degenerate
return -1; // do not deal with this case
Vector dir(R.P1(), R.P0()); // ray direction vector
Vector w0(R.P0(),T.V0());
a = - n.dot(w0);
b = n.dot(dir);
if (fabs(b) < SMALL_NUM) { // ray is parallel to triangle plane
if (a == 0) // ray lies in triangle plane
return 2;
else return 0; // ray disjoint from plane
}
// get intersect point of ray with triangle plane
r = a / b;
if (r < 0.0) // ray goes away from triangle
return 0; // => no intersect
// for a segment, also test if (r > 1.0) => no intersect
I.setCoordonne(R.P0().x() + r * dir.x(), R.P0().y() + r * dir.y(),R.P0().z() + r * dir.z()); // intersect point of ray and plane
// is I inside T?
float uu, uv, vv, wu, wv, D;
uu = u.dot(u);
uv = u.dot(v);
vv = v.dot(v);
Vector w(I,T.V0());
wu = w.dot(u);
wv = w.dot(v);
D = uv * uv - uu * vv;
// get and test parametric coords
float s, t;
s = (uv * wv - vv * wu) / D;
if (s < 0.0 || s > 1.0) // I is outside T
return 0;
t = (uv * wu - uu * wv) / D;
if (t < 0.0 || (s + t) > 1.0) // I is outside T
return 0;
return 1; // I is in T
}
