func TriangleIntersection(V1, V2, V3, O, D mgl.Vec3) (out float32, hit bool) {
const EPSILON = 0.000001
var e1, e2 mgl.Vec3 //Edge1, Edge2
var P, Q, T mgl.Vec3
var det, inv_det, u, v, t float32
//Find vectors for two edges sharing V1
e1 = V2.Sub(V1)
e2 = V3.Sub(V1)
//Begin calculating determinant - also used to calculate u parameter
P = D.Cross(e2)
//if determinant is near zero, ray lies in plane of triangle
det = e1.Dot(P)
//NOT CULLING
if det > -EPSILON && det < EPSILON {
return 0, false
}
inv_det = 1 / det
//calculate distance from V1 to ray origin
T = O.Sub(V1)
//Calculate u parameter and test bound
u = T.Dot(P) * inv_det
//The intersection lies outside of the triangle
if u < 0 || u > 1 {
return 0, false
}
//Prepare to test v parameter
Q = T.Cross(e1)
//Calculate V parameter and test bound
v = D.Dot(Q) * inv_det
//The intersection lies outside of the triangle
if v < 0 || u+v > 1 {
return 0, false
}
t = e2.Dot(Q) * inv_det
if t > EPSILON { //ray intersection
return t, true
}
// No hit, no win
return 0, false
}
