Raycast Triangle
Raycasting against a triangle is a three step process:
Create a plane from the three points of the triangle
Raycast against that plane
Check if the Raycast result is inside the triangle
We already have functions to implement this entire process. The FromTriangle function will create a plane from the triangle. We already have a Raycast function that casts a ray against a plane. We also have a PointInTriangle function.
We can improve the performance of the Raycast by using barycentric coordinates instead of the existing PointInTriangle test. Barycentric coordinates are a way to represent the position of a point relative to a triangle.
Getting ready
We are going to implement a new function, Barycentric. This new function will return the barycentric coordinates of a point with respect to a triangle. We will use this new function, along with the existing FromTriangle and Raycast functions created in Chapter 10, 3D Line Intersections to make a new Raycast against triangle function.
