How do I debug a shader?

Debugging a shader is a bit complicated because it’s running on the GPU.  Typically there’s no easy communication back to the CPU from the GPU. Shaders don’t provide a “printf” command to output debugging information to a console.

However, there are some options:

• In the fragment shader, set the fragment to a specific colour when a bug occurs (a shader version of “printf”)
• Use transform feedback to debug vertex shaders
• Use a debugging tool like Nvidia Nsight
• There are other tools like Shader Maker that can be used to develop shaders

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