OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Geometry Shader Redux

To use a geometry shader in your program:

• Create a geometry shader with glCreateShader(GL_GEOMETRY_SHADER).

• Set the shader source with glShaderSource and compile it with glCompileShader.

• Attach it to a program object with glAttachShader, and link the program with glLinkProgram.

Inside your geometry shader do the following:

• Specify input and output primitive types with the layout (<primitive_type>) in ; or layout (<primitive_type>) out ; layout qualifiers.

• Specify the maximum number of vertices the shader might produce with the layout (max_vertices = <vertex_count>) in ; layout qualifier.

• Declare all inputs to the geometry shader as arrays (using the in keyword). You can use the .length() method on the input arrays ...