Fixes OcclusionQuery for Android.GL

[squarebananas]

Fixes OcclusionQuery for Android with GLES.

QueryTarget.SamplesPassed is only available for OpenGL, not GLES. However, QueryTarget.SamplesPassedExt is supported for GLES, but only returns a result of 0 or 1 (where 1 represents one or more pixels visible) instead of the actual pixel count.

Although labelled as an extension, it is a core feature of GLES 3 and only an extension for GLES 2. Both names use the same enum value.

For GLES 2 (https://registry.khronos.org/OpenGL/extensions/EXT/EXT_occlusion_query_boolean.txt):

ANY_SAMPLES_PASSED_EXT 0x8C2F

For GLES 3 (https://registry.khronos.org/OpenGL/api/GLES3/gl3.h):

#define GL_ANY_SAMPLES_PASSED 0x8C2F

For testing, the XNA Lens Flare sample with Kni projects added can be found here: kniEngine/XNAGameStudio#1

[nkast]

I see that we had 0x8C2F incorrectly named SamplesPassedExt, but it's a different type of query (AnySamplesPassed) that returns a boolean, and not an extension of SamplesPassed.

The Lens Flare sample depend on PixelCount returning the number of pixels, and it's not a simple check of (PixelCount>0).

occlusionAlpha = Math.Min(occlusionQuery.PixelCount / queryArea, 1);

I see that you adjusted querySize in the sample , and documented the PixelCount behavior for GLES/WebGL.

However I imagine that people who port similar projects to Android/Web/Oculus, might have a hard time spotting the difference in behavior. I think it is best for PixelCount to throw a PlatformNotSupported.
We could add a new Property to the OcclusionQuery to support the limited functionallity of GLES, something like AnyPixelPassed, IsOccluded, or something similar.

[squarebananas]

I think it is best for PixelCount to throw a PlatformNotSupported.
We could add a new Property to the OcclusionQuery to support the limited functionallity of GLES, something like AnyPixelPassed, IsOccluded, or something similar.

Ok, I'll change PixelCount to PlatformNotSupportedException and add a new AnyPixelPassed property. I'll probably rename private _pixelCount to _queryResultValue as well.

[nkast]

So, this fails, because of Blazor.
Should I merge this now , add a stub to get it compile, and rebase/resolve the WebGL PR later?

[squarebananas]

So, this fails, because of Blazor. Should I merge this now , add a stub to get it compile, and rebase/resolve the WebGL PR later?

You mean because this PR would require #2599 and that would need BlazorGL to have the newer Wasm nuget versions for that? It will probably be fine to leave this blocked until then, but I've just added a stub in case anyway.

[nkast]

That's great. Merging.