Fix webgl2

[atlv24]

Objective

• Environment Map Filtering GPU pipeline #19076 (comment) broke webgl2 and bloated binary size by a megabyte
• Fixes WebGL2 broken: no compute shaders #20276

Solution

• Don't embed stbn.ktx2, just load it for now
• Gate gen env maps by limit checks
• Extract a plugin to do this cleanly
• Only load stbn.ktx2 when its needed

Testing

• reflection_probes example
• someone please test webgl2

[rparrett]

This would require users to download stbn.ktx2 and place it in their own assets/textures directory, which is probably not what we want.

[mate-h]

Thank you for the quick turnaround. I tested the reflection probe example on mac, webgpu and webgl. All works as expected. The diff also looks good to me but good point about using assets/textures folder.
Current and future use cases for the blue noise:

• realtime environment map filtering GGX
• solari path tracing and ReSTIR GGX
• raymarching algorithm jittering for volumetrics, atmosphere

A couple of solutions i have in mind:

• in the immediate term, to address the issue with the Bevy build output binary size the keep thus current PR as is
• we maybe need to generate the bluenoise at runtime on the CPU, however could introduce a new dependency or new code to maintain.
• just reduce the overall size of the bluenoise to 32x32 and keep it always in the binary
• hide it behind a feature flag. This means use cases I mentioned above would need to be run with the feature flag enabled

[atlv24]

Id rather leave improving DX to another PR, given that the alternative atm is a revert. I have a few ideas but im not sure which is best. Any are better than a revert though :p

[superdump]

I think this is fine. The plugin naming is not something I will block on but if people agree with me then it would be nice to change before merging.

One idea for a follow-up - we could add a feature to optionally compile-in the texture instead of loading it from an asset directory. That would give people the option of that convenience, though perhaps it has other downsides like ram usage for the binary, unless that part can be paged out after upload to vram.

[andriyDev]

Could we make this a system rather than a FromWorld impl? Something like init_blue_noise

[atlv24]

it seemed to be pretty sensitive to ordering, i dont want to figure out porting this to RenderStartup in this PR

[IceSentry]

Yeah, I'm okay with porting it later

[mate-h]

Removed this declaration for FromWorld and put the code block back into PBR plugin with a conditional feature flag.

[IceSentry]

I would prefer if the texture was embedded but gated by a feature flag and if someone spawns a GeneratedEnvironmentMapLight component without the feature flag we log a warning saying they need to enable the feature. A bit like what the tonemapping_luts feature flag does. The current approach requires user to copy the texture which is a bit less nice but not a blocker.

With that said, the PR as is does fix the issue, we can always implement the feature flag thing later.

[mate-h]

I created a PR against this branch to address some of @IceSentry feedback about using feature flags. I also added a fallback to a RNG based noise which still looks decent. Since this PR already has all approvals I don't consider this a blocker, can be reviewed/merged as a separate PR as well. I will get feedback on my proposed changes from @atlv24 when I get a chance.

[github-actions]

You added a new feature but didn't update the readme. Please run cargo run -p build-templated-pages -- update features to update it, and commit the file change.

[alice-i-cecile]

Shouldn't we be enabling this feature in other features, e.g. for solari or env maps?

[atlv24]

Its not needed in solari just yet, we'll let Jasmine add the feature when she starts using it. And gen env maps dont need this either thanks to the fallback, so for now its fine i believe

[atlv24]

@mate-h thanks for fixing CI! i think we're good to go