How to debug a GLSL shader?

Question

I need to debug a GLSL program but I don\'t know how to output intermediate result. Is it possible to make some debug traces (like with printf) with GLSL ?

Answer 1

You can try this: https://github.com/msqrt/shader-printf which is an implementation called appropriately "Simple printf functionality for GLSL."

You might also want to try ShaderToy, and maybe watch a video like this one (https://youtu.be/EBrAdahFtuo) from "The Art of Code" YouTube channel where you can see some of the techniques that work well for debugging and visualising. I can strongly recommend his channel as he writes some really good stuff and he also has a knack for presenting complex ideas in novel, highly engaging and and easy to digest formats (His Mandelbrot video is a superb example of exactly that : https://youtu.be/6IWXkV82oyY)

I hope nobody minds this late reply, but the question ranks high on Google searches for GLSL debugging and much has of course changed in 9 years :-)

PS: Other alternatives could also be NVIDIA nSight and AMD ShaderAnalyzer which offer a full stepping debugger for shaders.