OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Toy Ball

Programmability is the key to procedurally defining all sorts of texture patterns. This next shader takes things a bit further by shading a sphere with a procedurally defined star pattern and a procedurally defined stripe. This shader was inspired by the ball in one of Pixar’s early short animations, Luxo Jr. This shader is quite specialized. It shades any surface as long as it’s a sphere. The reason is that the fragment shader exploits the following property of the sphere: The surface normal for any point on the surface points in the same direction as the vector from the center of the sphere to that point on the surface. This property is used to analytically compute the surface normal used in the shading calculations within the fragment ...