/**
* Intersect the given Ray with this shape. Tests for every triangle of the shape. Speed depends
* hence on the complexity of the shape.
*
* @param Ray ray The Ray to be intersected
* @param Matrix4f transformation The transformation of the Shape into its actual position
* @return a RayShapeIntersection with the coordinates of the HitPoint if any.
*/
public RayShapeIntersection intersect(Ray ray, Matrix4f transformation) {
RayShapeIntersection intersection = new RayShapeIntersection();
List<RayShapeIntersection> hitTriangles = new ArrayList<RayShapeIntersection>();
// get all triangles
Iterator<Triangle> it = getTriangles().iterator();
Triangle triangle;
// calculate intersection of ray and triangle
while (it.hasNext()) {
triangle = it.next();
triangle.transform(transformation);
intersection = calculateIntersection(ray, triangle);
if (intersection.hit) {
hitTriangles.add(intersection);
}
}
Vector3f distance = new Vector3f();
float shortestDist = Float.MAX_VALUE;
for (RayShapeIntersection in : hitTriangles) {
distance.sub(ray.getOrigin(), in.hitPoint);
if (distance.length() < shortestDist) {
intersection = in;
shortestDist = distance.length();
}
}
// return the intersected point if any
return intersection;
}
private RayShapeIntersection calculateIntersection(Ray ray, Triangle triangle) {
RayShapeIntersection intersection = new RayShapeIntersection();
Vector3f u = new Vector3f();
Vector3f v = new Vector3f();
u.sub(triangle.mY, triangle.mX);
v.sub(triangle.mZ, triangle.mX);
Vector3f n = new Vector3f();
n.cross(u, v);
if (n.epsilonEquals(mZeroVector, mEpsilon)) {
// Triangle is either a point or a line (degenerate)
// Don't deal with this case
return intersection;
}
Vector3f w0 = new Vector3f();
w0.sub(ray.getOrigin(), triangle.mX);
float a = -n.dot(w0);
float b = n.dot(ray.getDirection());
if (Math.abs(b) < mEpsilon) { // ray is parallel to triangle plane
if (a == 0) {
// ray lies in triangle plane
return intersection;
} else {
// ray disjoint from plane
return intersection;
}
}
float r = a / b;
if (r < 0.f) {
// ray goes away from triangle
return intersection;
}
intersection.hit = true;
intersection.hitPoint = new Vector3f();
intersection.hitPoint.scaleAdd(r, ray.getDirection(), ray.getOrigin());
// Is intersection inside the triangle?
Vector3f w = new Vector3f();
w.sub(intersection.hitPoint, triangle.mX);
float uu, uv, vv, wu, wv, D;
uu = u.dot(u);
uv = u.dot(v);
vv = v.dot(v);
wu = w.dot(u);
wv = w.dot(v);
D = uv * uv - uu * vv;
// get and test parametric coordinates
float s, t;
s = (uv * wv - vv * wu) / D;
if (s < 0.f || s > 1) {
// I is outside T
intersection.hit = false;
intersection.hitPoint = null;
return intersection;
}
t = (uv * wu - uu * wv) / D;
if (t < 0.0 || (s + t) > 1.0) {
// I is outside T
intersection.hit = false;
intersection.hitPoint = null;
return intersection;
}
return intersection;
}
