OpenGL 4 Shading Language Cookbook - Third Edition

How to do it...

To create a shader program that can be used to render point primitives as quads, use the following steps:

1. The vertex shader will convert the position to camera coordinates and assign to the gl_Position output variable. Note that we're not converting to clip coordinates just yet:

layout (location = 0) in vec3 VertexPosition;uniform mat4 ModelViewMatrix;void main(){    gl_Position = ModelViewMatrix * vec4(VertexPosition,1.0);}

2. The geometry shader emits two triangles as a triangle strip. We use the gl_in variable to access the position from the vertex shader (camera coordinates): 

layout( points ) in; layout( triangle_strip, max_vertices = 4 ) out; uniform float Size2; // Half the width of the quad uniform mat4 ProjectionMatrix; ...