Question Why do constant buffers require compute shader support?

I noticed that creating a constant buffer using

new GraphicsBuffer(GraphicsBuffer.Target.Constant ... )

on a platform that doesn't support compute shader fails with this error:

Attempting to create a graphics buffer that requires compute shader support, but compute shaders are not supported on this platform. Target: Constant

My question is why do constant buffers require compute shader support? I am personally using them only to upload data to a non-compute (regular) shader, and I believe constant buffers are the most widely supported ways to upload data to a shader.

 

Hi, I'm not sure how to answer your question. Maybe it was added along with compute shader support, so older GPU or drivers don't support it.

You can check the #pragma documentation.


If you only need to read the data, I think you can try (uncompressed) texture sampling?

 

Which platform is that?

 

@wwWwwwW1 The OP's question is about GraphicsBuffers, not specifically structured buffers / compute buffers. They're different (though compute buffers can also be used as constants now).

Unity's own documentation has this to say about a constant GraphicsBuffer:

https://docs.unity3d.com/ScriptReference/GraphicsBuffer.Target.html
That would imply they should work even without compute shader support, which means that error is likely a bug.

@MateiGiurgiu I would suggest reporting this as a bug via the in-editor bug reporting menu.

 

Not all platforms support constant buffers. At the very least GLES 2.0 and DX9 don't. If either of those are your target the bug is actually the message, not the fact it doesn't work.

 

We are not supporting GLES 2.0 and neither DX9. This issue happened on a GLES 3.0 device with shader level 3.5.

 

AFAIK constant buffers need shader model 4.0 at the very least.