OpenGL 4 Shading Language Cookbook - Third Edition

How to do it...

To create a shader program that discards fragments based on a square lattice (as in the preceding image):

1. In the vertex shader, we use two-sided lighting, and include the texture coordinate:

layout (location = 0) in vec3 VertexPosition; 
layout (location = 1) in vec3 VertexNormal; 
layout (location = 2) in vec2 VertexTexCoord; 
 
out vec3 FrontColor; 
out vec3 BackColor; 
out vec2 TexCoord; 
// Other uniform variables here...
// getCamSpace and phongModel functions... 
void main() { 
    TexCoord = VertexTexCoord;
 
    // Get the position and normal in camera space  vec3 camNorm, camPosition; getCamSpace(camNorm, camPosition); FrontColor = phongModel( camPosition, eyeNorm ); BackColor = phongModel( camPosition, -eyeNorm ); gl_Position = MVP ...