Check autoClear for RTT to fix utility layer on native OpenXR #12774
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Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s). |
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Snapshot stored with reference name: Test environment: To test a playground add it to the URL, for example: https://babylonsnapshots.z22.web.core.windows.net/refs/pull/12774/merge/index.html#WGZLGJ#4600 Links to test babylon tools with this snapshot: https://playground.babylonjs.com/?snapshot=refs/pull/12774/merge To test the snapshot in the playground with a playground ID add it after the snapshot query string: https://playground.babylonjs.com/?snapshot=refs/pull/12774/merge#BCU1XR#0 |
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LGTM but will wait on @RaananW to validate :-) |
Former-commit-id: 3faa363da681e0de8a7567594d9bd5f906053298
Illustration showing left and right eyes in a HoloLens 2 running BabylonNative:
fixes BabylonJS/BabylonNative#1087
There were two issues going on here. The first is that we needed to render the utility layer after rendering to both eyes in the target scene. By rendering the utility layer scene in between eye renders, we were getting weird clearing behavior that is hard to describe. The second is that we were double-clearing our output render target textures in cases where
RenderTargetTexture.skipInitialClear = false.By changing the observable used in
utilityLayerRendererfromonAfterCameraRenderObservabletoonAfterRenderCameraObservable, we're making sure to render the layer only once after finishing both eyes (instead of after the left and before the right and then again after both eyes). This doesn't meaningfully change any behavior in rendering scenarios with cameras without sub-cameras.By checking
Scene.autoClearwhen clearing the camera's output render target, we avoid clearing our render targets when rendering multiple scenes that are supposed to layer onto those render targets. This means that clearing behavior when rendering a scene to a render target matches the clearing behavior when rendering that same scene to the default frame buffer. This is a breaking change for experiences that expected the scene not to honorautoClear = falsewhen rendering to a RTT, but this is not documented/expected behavior as far as I know.We weren't seeing this bug in any other scenario (i.e. Oculus on Web, native iOS, native Android, etc) because on all other platforms
RenderTargetTexture.skipInitialClear = true, and so we never saw any weird clearing behavior because the RTT's were never getting cleared in the first place, which on those platforms is totally acceptable because they get automatically cleared by either the WebXR runtime or the BabylonNative XR implementation at the top of the frame.