OpenGL 4 Shading Language Cookbook - Third Edition

How to do it...

To create a shader program that utilizes the geometry shader to produce a wireframe on top of a shaded surface, use the following steps:

1. Use the following code for the vertex shader:

layout (location = 0 ) in vec3 VertexPosition; 
layout (location = 1 ) in vec3 VertexNormal; 
 
out vec3 VNormal; 
out vec3 VPosition; 
 
uniform mat4 ModelViewMatrix; 
uniform mat3 NormalMatrix; 
uniform mat4 ProjectionMatrix; 
uniform mat4 MVP; 
 
void main() {
    VNormal = normalize( NormalMatrix * VertexNormal); 
    VPosition = vec3(ModelViewMatrix *  
                     vec4(VertexPosition,1.0)); 
    gl_Position = MVP * vec4(VertexPosition,1.0); 
} 

2. Use the following code for the geometry shader:

layout( triangles ) in; layout( triangle_strip, max_vertices = 3 ) out; out vec3 GNormal; ...