I've been implementing frustum culling in an OpenGL application that appears to be working correctly.

The issue I have been having when trying to render the frustum shape from the camera, my debug lines appear to only outline the application window borders. When the application starts I would see the four yellow debug lines in a rectangular pattern around the OpenGL window, but nothing else related to the frustum.

I managed to get the frustum shape to render in a previous attempt, but it would not stay with the camera's movement.

GitHub link: https://github.com/JoshTyra/OpenGLFrustum_Culling

I have tried different methods that I could find online, and in papers covering this topic. Beare in mind some of the code was experimental.