
CHAPTER 4 ■ WORKING WITH MODELS
388
This verifies that the collision point is on the same side of each boundary of the tri-
angle, by checking whether the cross vectors have the same direction. This is verified in the
CompareSigns method:
private bool CompareSigns(Vector3 first, Vector3 second)
private bool CompareSigns(Vector3 first, Vector3 second)
{
if (Vector3.Dot(first, second) > 0)
return true;
else
return false;
}
4-19. Detect Whether the Pointer Is Over a Model
The Problem
You want to detect whether the user’s pointer is over a Model in your 3D scene.
The Solution
In XNA, it’s easy to retrieve the 2D position of the pointer on the screen. However, ...