WebGPURenderer: Introduce Shadow Map Array

[RenaudRohlinger]

By combining RenderBundle, ArrayCamera, RenderTargetArray, and a new DepthArrayTexture and FrustumArray, this PR opens the door to rendering multiple shadow passes in a single, highly performant render.

I’ve added a new example along with a TileShadowNode to demonstrate a foundational use case that takes advantage of this feature. In the example, the scene is divided into four sections, enabling a 16K resolution shadow map at nearly the same cost as 8K. This technique bypasses the 8K resolution limit, improves performance, and avoids the 16-sampler bind limit.

Looking ahead, it would be great to update nodes like CSM to leverage this new feature, especially since CSM already uses multiple FBOs at the same resolution, making it a perfect match. We could even implement a Tiled CSM system for open-world scenes, now that we can scale up to a 2048 shadow map limit per program.

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TODO:

• WebGL Support
• Move TileShadow Helpers to a new TileShadowNodeHelper class
• Support Frustum Culling for ArrayCamera in the Renderer -> Introduce FrustumArray
• [] Support VSM Shadows in TileShadow

@sunag Feedbacks and help on the node part would be greatly appreciated!

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This contribution is funded by Renaud Rohlinger @ Utsubo

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.36 78.34	336.39 78.35	+31 B +9 B
WebGPU	533.31 148.2	540.64 149.78	+7.33 kB +1.58 kB
WebGPU Nodes	532.77 148.1	540.1 149.68	+7.33 kB +1.58 kB

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	465.37 112.21	465.37 112.21	+0 B +0 B
WebGPU	604.89 164.17	613.53 165.84	+8.64 kB +1.67 kB
WebGPU Nodes	559.88 153.6	568.52 155.25	+8.64 kB +1.65 kB

[RenaudRohlinger]

@sunag I also added Frustum support for ArrayCamera via a new FrustumArray class. I’ve tested everything on both backends (Windows and macOS), and it all looks good so far.

I’ll move on to finishing VSM shadows in TileShadow, depending on your feedback, just want to avoid working on something that might get changed if you’re planning to work some magic on the TileShadow node side.

Would be awesome if you could take a look at the node when you get a chance! 🙇

[Spiri0]

This would probably be a PR. Since this is about shadows, and I've been on the subject recently, I'm just asking.
Is it possible to use your shadowTexture in a custom shader?
I have to create my own light source to make this work satisfactorily, because with the standard directional light, the update has a frame delay, and the shadows flicker as a result when you move.

[sunag]

It seems that the background with Cubemap without PMREM broke

[sunag]

Would be awesome if you could take a look at the node when you get a chance! 🙇

I tried to help with some details, the PR is amazing, it will certainly be very useful <3

[RenaudRohlinger]

Overall the PR should be good now.
Regarding VSM I checked but by definition VSM doesn't seem really compatible with the tile logic or it would be better to work on it in another PR if someone find somehow a compatibility.

I wanted to throw an error when using VSMShadowMap but I don't think I can do a check like:

const shadowMapType = builder.renderer.shadowMap.type;

if ( shadowMapType === VSMShadowMap ) {

	throw new Error( 'TileShadowNode: VSMShadowMap is not supported.' );

}

because the renderer is only accessible when the node gets build, not when instancing, resulting in AnalyticLightNode crashing while trying to read the custom shadow.shadowNode.

Also it feels too much like an edge case to pollute the code of AnalyticLightNode to fix this issue for such a small edge-case.

Would it be ok to just add a comment somewhere or ignore that case? /cc @sunag @Mugen87

[Mugen87]

I think you can mention the edge case in the JSDoc for TileShadowNode. That should make it clear.

[cmhhelgeson]

Is the TileShadowNodeHelper automatically rendered outside of the postProcessing pipeline or does that have to be configured via MRT.

[RenaudRohlinger]

The TileShadowNodeHelper is just a basic mesh in the scene, I just tricked the vertex shader to display it as a quad mesh, which means that it will be affected by the postProcessing pipeline. Also it's just a helper so I think it's fine.

[Mugen87]

@RenaudRohlinger Would it be possible to refactor getShadowRenderObjectFunction() so it does not return a new function object on every invocation? updateShadow() is called per frame per shadow casting light so this might affect GC overhead.