// Source http://geomalgorithms.com/a06-_intersect-2.html#intersect3D_RayTriangle%28%29
RayHit Triangle3d::CalculateCollision(Line3d line) {
float r, a, b; // params to calc ray-plane intersect
Vector3d dir = line.direction; // ray direction vector
Vector3d w0 = Vector3d(line.position, this->a);
a = -Vector3d::dotProduct(normal, w0);
b = Vector3d::dotProduct(normal, dir);
if(abs(b) < 0.000001f) { // ray is parallel to triangle plane
return RayHit(); // Disjoint. no intersect
}
// get intersect point of ray with triangle plane
r = a / b;
if(r < 0.0) // ray points away from triangle
return RayHit(); // => no intersect
// for a segment, also test if (r > 1.0) => no intersect
Point3d I = line.getPositionAlongLine(r); // intersect point of ray and plane
// is I inside T?
float uu, uv, vv, wu, wv, D;
uu = Vector3d::dotProduct(u, u);
uv = Vector3d::dotProduct(u, v);
vv = Vector3d::dotProduct(v, v);
Vector3d w = Vector3d(I, this->a);
wu = Vector3d::dotProduct(w, u);
wv = Vector3d::dotProduct(w, 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 RayHit();
t = (uv * wu - uu * wv) / D;
if(t < 0.0 || (s + t) > 1.0) // I is outside T
return RayHit();
return RayHit(I,normal); // I is in T
}
Color Trace(Ray& R, int lev) // trace a ray
{
RayHit hit = RayHit(MISS, 0, Vector(0, 0, 0), false);
if (lev > MAX_RECURSION_LEVEL)
return defColor;
int hitObj = -1;
for (int i = 0; i < nObjs; i++) {
RayHit h = theShapes[i]->intersect(R);
if (h.status != MISS && h.tValue < R.tValue) {
hitObj = i;
hit = h;
R.tValue = h.tValue;
}
}
if (hitObj < 0)
return defColor;
else
return Shade(hitObj, R, hit, lev);
}
