Allow ETC2 in OpenGL if ES3 compatible

[valaphee]

Connections

Description
ETC is also usable on Desktop GL if GL_ARB_ES3_compatibility is present. See https://registry.khronos.org/OpenGL/extensions/ARB/ARB_ES3_compatibility.txt

Testing
Skybox example with only ETC2 used.

Checklist

• Run cargo fmt.
• [ x Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[valaphee]

Btw, just noticed that ANY_SAMPLES_PASSED_CONSERVATIVE is theoretically also an ES3 feature, Should be replaced with ANY_SAMPLES_PASSED, but considering how few drivers don't support GL_ARB_ES3_compatibility...

[Wumpf]

huh super surprised this works given how rare etc support is on desktop e.g. according to the vulkan database, but that's what the GL_ARB_ES3_compatibility spec says should be possible!
Thanks!

[valaphee]

Just figured out that etc is supported on all platforms, starting with OpenGL 4.3, GL_ARB_ES3_compatibility is for OpenGL 4.2 and prior, but GL_ARB_ES3_compatibility is present anyway.

[teoxoy]

That seems to be on par with the findings in #5234.