CODEWITHSUNDEEP
iphoneiosopengl-es-2.0glsl
hanno
hanno

Reputation: 6513

Implementation limit of active vertex shader samplers on the iPhone

I'm trying to use a sampler in a vertex shader on the iPhone. The documentation says that this is not supported on the PowerVR SGX. However, it seems that at least someone got it working in the simulator, although not without problems.

When I try to run this in the simulator (iOS 6), I get the following error message while compiling the shaders:

ERROR: Implementation limit of 0 active vertex shader samplers 
(e.g., maximum number of supported image units) exceeded, 
vertex shader uses 1 samplers

What changed since the other question got asked? Did they just add a (correct!) error message? Or is it maybe possible to use a sampler in the vertex shader now? fingerscrossed...

Upvotes: 1

Views: 701

Answers (1)

Brad Larson
Brad Larson

Reputation: 170317

I had the exact same question, so I asked a couple of Apple's OpenGL ES engineers this at WWDC. According to them, the support for sampling from a texture within a vertex shader on certain devices in iOS 4.x was a bug, and this was removed in iOS 5.x.

It has never been officially supported, and this new error message is just describing why this fails. On iOS 5.x, and most devices running iOS 4.x, you'd just get a black screen if you tried this, with no warnings. All they've done is add some explanation for this behavior.

Upvotes: 2

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