[Mathematics] BoundingFrustum.Intersects(...Ray...) not working correctly

[deng0]

I've stumbled upon a problem with the BoundingFrustum Ray intersection method.

In the case where the Ray.Position is not contained within the BoundingFrustum, the method does not work correctly in many cases:
The idea that is used (check whether middle position of min/max ray-plane-intersections is inside frustum) is not correct.
In many cases there are more than two ray-plane-intersections and the middle position is not meaningful.

Also some other notes about BoundingFrustum:

• In the first case where the Ray.Position is contained within the BoundingFrustum, shouldn't the inDistance be set to 0 and the outDistance to nearstPlaneDistance instead of inDistance to nearstPlaneDistance and outDistance to null.
• Perhaps the method bool Intersects(ref Ray ray), where we don't care about inDistance and outDistance, could use a different more efficient implementation.
• The method Contains(Vector3[] points) throws a NotImplementedException, perhaps it's better to remove the method instead.

[deng0]

Another small issue with Collision.RayIntersectsTriangle():
If the triangle is very small and therefor the edges of the triangle are very short MathUtil.IsZero(determinant) is true although the ray is not at all parallel to the triangle plane.