I'm in the process of debugging GLSL vertex shaders and I can't shake the feeling that I'm doing it wrong.

In general I have two strategies to make up for the lack of tracing

  • I stuff values into a debug color varying that I pass to the fragment shader and then try to interpret the colors.
  • I change the vertex shader code and see what happens.

I'm thinking that ideally I could make up for the lack of tracing by writing values to a texture somehow, reading the texture from the GPU and printed the values stuffed in the texture.

My guess is that there might be way better ways. Any suggestions?


2 Answers 2


A friend of mine has used glslDevil for this, and said it was okay.

If you're not tied to GLSL, Microsoft has an incredible tool for DirectX called PIX, but I don't think there's anything equivalent for OpenGL.

  • \$\begingroup\$ I've downloaded glslDevil but I can't get most of the features to work. The tracing works, and the stepping through shaders but I can't see the values of variables. \$\endgroup\$ Commented Nov 10, 2010 at 16:31

nVidia has an awesome shader debugger. You can find it, and its specs, HERE

Update 2016: There is also a Visual Studio plugin, which most probably is their newer effort in helping developers, here: https://developer.nvidia.com/nvidia-nsight-visual-studio-edition

  • \$\begingroup\$ typo: its specs \$\endgroup\$
    – o0'.
    Commented Nov 10, 2010 at 14:20
  • \$\begingroup\$ thx. =) I get those right 70% of the time. I blame DainBramage. \$\endgroup\$
    – Nailer
    Commented Nov 10, 2010 at 15:35
  • \$\begingroup\$ no GLSL support though :(, but it looks like I can convert cg shaders to glsl automatically, might give that a try. \$\endgroup\$ Commented Nov 10, 2010 at 16:30
  • \$\begingroup\$ You're right about that, but I think the advantages outweights the disadvantages. Besides, FX composer is a pretty nifty app. \$\endgroup\$
    – Nailer
    Commented Nov 10, 2010 at 19:53
  • \$\begingroup\$ Broken link.... \$\endgroup\$
    – UpTheCreek
    Commented Jan 13, 2017 at 8:57

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