Triangle to triangle

Testing if two triangles intersect is done using a generic SAT test. We will have to test a total of 11 axes. These axes are:

• The normal of the first triangle
• The normal of the second triangle
• The cross product of the edges of each triangle
  

Getting ready

We need to implement a new OverlapOnAxis test as well as the actual SAT test. The actual SAT test will be performed inside the TriangleTriangle collision function. We first covered the Separating Axis Theorem in Chapter 5, 2D Collisions. In this section we will check 11 axes of potential separation. If any axis of separation is found, the triangles do not intersect.

How to do it…

Follow these steps to check if two triangles intersect:

1. Declare the OverlapOnAxis and TriangleTriangle function in Geometry3D.h:

   bool OverlapOnAxis(const Triangle& t1, 
       const Triangle& t2, const vec3& axis);
   bool TriangleTriangle(const Triangle& t1, 
       const Triangle& t2);

2. Implement the OverlapOnAxis function in Geometry3D...