Limit on SampleCount for MSAA?

[Jean-Colas Prunier]

I have been successfully testing the use of sampleCount with the value set to 4 (on the texture and the depth stencil). But if I set the value to 8 for example, I get an error message (Validation error: The sample count (8) of the texture is not supported).

I looked whether it was possible to get the maxSampleCount for the card I am using. Is there a way of doing this using the adapter? is there a current limit set to 4 (basically it's either 1 or 4?).

Thank you for your input. -jc

[Mark Sibly]

> is there a current limit set to 4 (basically it's either 1 or 4?).

From the sound of this thread, I think your choices here are indeed limited to 1 or 4:

https://github.com/gfx-rs/wgpu/issues/2586

Not really sure what the 'lowest-common-denominator' standard for multisampling is these days, but surely it's >4? Probably not hard to hack dawn to support more anyway.

[Corentin Wallez]

That's correct, 1 and 4 are the only allowed values for sampleCount at the moment because that's the only portable option. See the initial investigation here. Soon after V1 the group will look at defining an API for optional texture capabilities that will be sure to include higher sample count textures. WGPU already has something like that which includes MSAA 2x and MSAA 8x. You can hack the validation of the multisample count away, or try adding an extension for 8x MSAA (but we might not be able to upstream that quickly just because we'd like to piggyback on what the WebGPU group decides for optional texture capabilities).

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[Jean-Colas Prunier]

Thank you both.

The linked documents are very useful. Many thanks for that.

As usual, perfectly happy with what's currently there. It will be greater later indeed to extend to 8/16...