[Mesa-users] glGetUniformLocation returns -1 for most uniforms

[Jonas Kulla]

Have you made sure that the uniforms are actually used in the shader? If
they're not, the compiler is free to optimize them out and return -1 for
their location, as it doesn't change runtime behavior.

2014-09-23 5:17 GMT+02:00 Joel Leclerc <lkjoel at ubuntu.com>:

> Normally, I use the proprietary nvidia GL driver to test my application,
> but now that I use the mesa backend, for some reason, glGetUniformLocation
> returns -1 on certain uniforms (for reasons I can't comprehend).
>
> Here is part of my shader source:
>
> uniform mat4 N_MVP;
> uniform bool N_UV_flip;
> uniform float N_UV_z;
> uniform float N_alpha;
> uniform bool N_3D;
> uniform float N_time;
> uniform float N_rand;
>
> If I run glGetUniformLocation(shader->shader_handle, "N_rand"), it returns
> -1. same for N_time, and N_UV_z. However, using the same code for N_alpha
> returns 2.
>
> This does not happen on the nvidia GL driver.
>
> Any clues as to why? Source code is available here:
> https://github.com/MiJyn/nightmare and
> https://github.com/MiJyn/silentponyville .
>
> --
> Joel Leclerc
> Individual software and game developer,
>    Lead developer of the SythOS project.
> Main email: lkjoel at ubuntu.com | Chat: lkjoeldev at gmail.com
> Twitter: @__MiJyn__ <https://twitter.com/__MiJyn__> | Website:
> http://mijyn.github.io/
> Github: https://github.com/MiJyn
>
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>
>
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