public static bool Intersect(Ray ray, Plane plane, out float distance){
// ray: {x | x = p + t * d}
// plane: {x | x dot n + D = 0}
// solve for t:
// (p + t * d) dot n + D = 0
// (t * d) dot n = (-(p dot n)-D) / (d dot n)
float dotDir = Vector3.Dot(ray.Direction , plane.Normal);
if (Math.Abs (dotDir) < Precission) {
distance = 0;
return false;
}
float dotPos = Vector3.Dot(ray.Position , plane.Normal);
float t = (-dotPos - plane.D) / dotDir;
if (t < 0.0f) {
if (t < -Precission) {
distance = 0;
return false;
} else {
// consider it intersection at 0
t = 0.0f;
}
}
distance = t;
return true;
}
public static bool Intersect(Ray ray, BoundingSphere sphere, out float distance){
Vector3 diff = sphere.Center - ray.Position;
float dd = (diff).LengthSquared;
float rr = sphere.Radius * sphere.Radius;
// check if ray point is inside sphere
if ( dd < rr){
distance = 0.0f;
return true;
}
float dot = Vector3.Dot (diff, ray.Direction);
if (dot < 0.0) {
distance = 0.0f;
return false;
}
// temp = ||diff||^2 - ||diff||^2 cos^2(theta)
// temp = ||diff||^2 sin^2(theta)
float temp = dd - dot * dot;
if (temp > rr) {
distance = 0.0f;
return false;
}
distance = dot - (float)Math.Sqrt(rr - temp);
return true;
}
public static bool Intersect(Ray ray, BoundingBox box, out float distance){
// current minimum t to get inside
float t = 0.0f;
// max t before going outside in one dim
float tmax = float.MaxValue;
for (int dim = 0; dim < 3; dim++) {
if (Math.Abs (ray.Direction [dim]) < Precission) {
// parallel to X face
if (ray.Position [dim] < box.Minimum [dim] || ray.Position [dim] > box.Maximum [dim]) {
distance = 0.0f;
return false;
}
} else {
// ray eq:
// p = p0 + t * d
// t = (p.x - p0.x)/d.x
float tin = (box.Minimum [dim] - ray.Position [dim]) / ray.Direction [dim];
float tout = (box.Maximum [dim] - ray.Position [dim]) / ray.Direction [dim];
if (tin > tout) {
float aux = tin;
tin = tout;
tout = aux;
}
t = Math.Max (tin, t);
tmax = Math.Min (tout, tmax);
if (t > tmax) {
// is out of another dim when entering this one.
distance = 0.0f;
return false;
}
}
}
distance = t;
return true;
}
public static bool Intersects(BoundingBox box, Ray ray, out float distance){
return Ray.Intersect (ray, box, out distance);
}
public static bool Intersects(BoundingSphere sphere, Ray ray, out float distance){
return Ray.Intersect (ray, sphere, out distance);
}
