/**
* Tests this surface for intersection with ray. If an intersection is found record is filled out
* with the information about the intersection and the method returns true. It returns false
* otherwise and the information in outRecord is not modified.
*
* @param outRecord the output IntersectionRecord
* @param ray the ray to intersect
* @return true if the surface intersects the ray
*/
public boolean intersect(IntersectionRecord outRecord, Ray rayIn) {
// TODO(B): fill in this function.
// Hint: This object can be transformed by a transformation matrix.
// So the rayIn needs to be processed so that it is in the same
// coordinate as the object.
Ray ray = untransformRay(rayIn);
double ax = owner.getVertex(index[0]).x;
double ay = owner.getVertex(index[0]).y;
double az = owner.getVertex(index[0]).z;
double px = ray.origin.x;
double py = ray.origin.y;
double pz = ray.origin.z;
double dx = ray.direction.x;
double dy = ray.direction.y;
double dz = ray.direction.z;
// calculating t, gamma, and beta based on linear system presented in
// Shirley and Marschner
double ei_hf = e * dz - dy * f;
double gf_di = dx * f - d * dz;
double dh_eg = d * dy - e * dx;
double ak_jb = a * (ay - py) - (ax - px) * b;
double jc_al = (ax - px) * c - a * (az - pz);
double bl_kc = b * (az - pz) - (ay - py) * c;
double m = a * ei_hf + b * gf_di + c * dh_eg;
double t = -(f * ak_jb + e * jc_al + d * bl_kc) / m;
if (t < ray.start || t > ray.end) {
return false;
}
double gamma = (dz * ak_jb + dy * jc_al + dx * bl_kc) / m;
if (gamma < 0 || gamma > 1) {
return false;
}
double beta = ((ax - px) * ei_hf + (ay - py) * gf_di + (az - pz) * dh_eg) / m;
if (beta < 0 || beta > 1 - gamma) {
return false;
}
if (outRecord != null) {
outRecord.t = t;
ray.evaluate(outRecord.location, t);
outRecord.surface = this;
if (norm == null) {
// interpolate normal based on barycentric coords
double alpha = 1.0 - gamma - beta;
Vector3 an = owner.getNormal(index[0]);
an.scale(alpha);
Vector3 bn = owner.getNormal(index[1]);
bn.scale(beta);
Vector3 cn = owner.getNormal(index[2]);
cn.scale(gamma);
Vector3 n = new Vector3(an.x + bn.x + cn.x, an.y + bn.y + cn.y, an.z + bn.z + cn.z);
outRecord.normal.set(n);
} else {
outRecord.normal.set(norm);
}
tMat.rightMultiply(outRecord.location);
tMatTInv.rightMultiply(outRecord.normal);
outRecord.normal.normalize();
}
return true;
}
