OpenGL 4 Shading Language Cookbook - Third Edition

How to do it...

To create a shader program that creates Bezier patches from input patches of 16 control points, use the following steps:

1. Use the vertex shader from the Tessellating a 2D quad recipe.
2. Use the following code for the tessellation control shader:

layout( vertices=16 ) out; 
 
uniform int TessLevel; 
 
void main() {
    // Pass along the vertex position unmodified 
    gl_out[gl_InvocationID].gl_Position =  
                 gl_in[gl_InvocationID].gl_Position; 
 
    gl_TessLevelOuter[0] = float(TessLevel); 
    gl_TessLevelOuter[1] = float(TessLevel); 
    gl_TessLevelOuter[2] = float(TessLevel); 
    gl_TessLevelOuter[3] = float(TessLevel); 
 
    gl_TessLevelInner[0] = float(TessLevel); 
    gl_TessLevelInner[1] = float(TessLevel); 
}

3. Use the following code for the tessellation evaluation ...