Using functions in shaders

The GLSL supports functions that are syntactically similar to C functions. However, the calling conventions are somewhat different. In the following example, we'll revisit the ADS shader using functions to help provide abstractions for the major steps.

Getting ready

As with previous recipes, provide the vertex position at attribute location 0 and the vertex normal at attribute location 1. Uniform variables for all of the ADS coefficients should be set from the OpenGL side, as well as the light position and the standard matrices.

How to do it...

To implement ADS shading using functions, use the following code:

1. Use the following vertex shader:

   layout (location = 0) in vec3 VertexPosition;
   layout (location = 1) in vec3 VertexNormal;
   
   out vec3 LightIntensity;
   
   struct LightInfo {
       vec4 Position; // Light position in eye coords.
       vec3 La;       // Ambient light intensity
       vec3 Ld;       // Diffuse light intensity
       vec3 Ls;       // Specular light intensity...