Raycast plane

To Raycast against a plane we must find a point which is on the plane being cast against and also along the normal of the ray. We know a point is on the surface of a plane if it satisfies the plane equation. If no point along the ray satisfies the plane equation, the ray and plane do not intersect:

Getting ready

We are going to implement a function that performs a Raycast against a plane. This function will return t, the time along the ray at which it intersects the plane. If there is no intersection, the value of t will be negative.

How to do it…

Follow these steps to implement raycasting against a plane:

1. Declare the Raycast function in Geometry3D.h:

   float Raycast(const Plane& plane, const Ray& ray);

2. Implement the Raycast function in Geometry3D.cpp:

   float Raycast(const Plane& plane, const Ray& ray) {
      float nd = Dot(ray.direction, plane.normal);
      float pn = Dot(ray.origin, plane.normal);

3. The nd variable must be less than zero for the ray to intersect the plane....