WebXRManager: Avoid invalid projection matrices when using depth sensing

[mrxz]

Related issue: #29098

Description

The depthFar and depthNear values coming from the depth-sensing module could result in invalid projection matrices (NaN values). These errors would propagate (left, right, XR and user camera) resulting in a broken state after exiting the XR session.

This PR includes three changes:

• Only recompute a union projection matrix when far plane is finite. In case of an infinite far plane, reuse the projection matrix of the left view. Offsetting the camera is sufficient to fully include both view volumes, assuming the projections are symmetric (see https://computergraphics.stackexchange.com/a/1737)
• Don't update the far and near properties of the user camera, instead always treat these as input to set the far/near of the renderState. When depth-sensing is active, the relevant depthNear/depthFar values are used for rendering, but not written back to the user-camera.
• Remove calls to updateProjectionMatrix added in 6e3137. These calls aren't needed, as the projection matrices for the left and right view come directly from the WebXR API and are computed in setProjectionFromUnion for cameraXR. In fact, as the comment above it indicates, the new far/near values only take effect next frame, so immediately computing them is incorrect for that frame.

This contribution is funded by Fern Solutions

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
685.1 kB (169.6 kB)	685.2 kB (169.6 kB)	+43 B

🌳 Bundle size after tree-shaking

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

Filesize dev	Filesize PR	Diff
462 kB (111.4 kB)	462 kB (111.4 kB)	+43 B

[Mugen87]

@cabanier Looking good?

[cabanier]

@cabanier Looking good?

Does this update the cameras for the left and right eye? It seems like only the main camera is updated and I seem to remember that one is only used to do culling.

[mrxz]

Does this update the cameras for the left and right eye?

Yes, their near/far are updated here (like before) and their projection matrices are taken from the XRView each frame. There should be no reason to manually (re)construct the projection matrices.

[cabanier]

Does this update the cameras for the left and right eye?

Yes, their near/far are updated here (like before) and their projection matrices are taken from the XRView each frame. There should be no reason to manually (re)construct the projection matrices.

Great! lgtm!