Limited number of varying?

OpenGL
1

Is there a restriction regarding the number of varying variables? I currently use 4 x vec3, 2 x vec2 and 2 x vec4. That works fine, but when I use another I get this error:

 
InfoLog:
(28) : error C5041: cannot locate suitable resource to bind parameter "diffuseProduct"
63 lines, 1 errors.


InfoLog:
(23) : error C5041: cannot locate suitable resource to bind parameter "diffuseProduct"
44 lines, 1 errors.


Failed to compile shader.
Error loading shaders.

That is even if its a single float. The target hardware is FX5950. I’ve tested with drivers 61.06 (Linux), 61.71 (win), 61.76 (win) and 62.20 (win). I can post the code if it helps.

2

In general, (for non-GeForce 6xxx hardware) 8 vector varyings is all you get. Smarter compilers will eventually be able to concatonate smaller varyings into larger ones. For example, the compiler has the ability to take your 2 vec2’s and use a single vec4 varying on it. However, glslang compilers are just trying to be compliant these days; eventually they’ll get around to more aggressive optimizations.

In the meantime, you can always do it yourself. Just use a vec4 instead of 2 vec2’s.

3

Thank you!

4

One more note. NV4x hardware supports 10 varying vectors, as I recall.

5

you can get the number of varying floats avalaible with the right glGet* (GL_MAX_VARYING_FLOATS_ARB, and GL_MAX_TEXTURE_COORDS_ARB) (you can have more varyings than texture interpolators, for example, you can have 8 texture interpolators, but 64 varying floats)

6

If you need more than 8, you can pass some data in color and secondary color too.

7

Great! Thanks alot!

8

It seems like we can never get away from hw specs entirely and have to rely on nv/ati set limits instead. Sucks imo.

9

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