Fixed image splitting in VR mode

[SorryNotSorryBasileus]

Fixed image splitting in VR #8137 according to http://paulbourke.net/stereographics/stereorender/. Tested in HTC Vive.

[cesium-concierge]

Thank you so much for the pull request @SorryNotSorryBasileus! I noticed this is your first pull request and I wanted to say welcome to the Cesium community!

The Pull Request Guidelines is a handy reference for making sure your PR gets accepted quickly, so make sure to skim that.

• ❌ Missing CONTRIBUTORS.md entry.
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[hpinkos]

@lilleyse or @tfili can you review this?

[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[OmarShehata]

I can confirm @SorryNotSorryBasileus has a signed CLA so this is good to start reviewing.

[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[Lastkraftwagen]

Who should be noted here to merge this fix? very useful changes for working with vr. Please, somebody with write access, megre this request.

[mramato]

@Lastkraftwagen I apologize for the slow response here. @lilleyse are you the best person to review this, or can you suggest someone else?

[Lastkraftwagen]

@lilleyse, I've asked @SorryNotSorryBasileus for permissions and resolved merge conflicts with CONTRIBUTORS.md. Can you merge this pull request, please?

[SorryNotSorryBasileus]

Couple of before-after screenshots.

[Lastkraftwagen]

I've tested the code, written by @SorryNotSorryBasileus , on Oculus CV1. Everything works correctly.

[lilleyse]

@SorryNotSorryBasileus @Lastkraftwagen thanks for the PR and screenshots. I have a Google Cardboard I'm going to try out.

My only code suggestion (right now) is to not allocate two PerspectiveOffCenterFrustum every frame. Is it possible to reuse a scratch PerspectiveOffCenterFrustum?

[lilleyse]

@SorryNotSorryBasileus I pushed some cleanup related changes in bec0617. I confirmed that after my changes it looks exactly the same as your changes. I still need to do a final test with the Cardboard but I expect to merge this tonight or tomorrow.

[lilleyse]

Something buggy is happening when scene.logarithmicDepthBuffer is false. I noticed it on my phone which doesn't support gl_FragDepth and falls back to multifrustum. I think it's only working for the closest frustum.

[emackey]

Off-topic, but someday it would be nice to deprecate this whole fake VR implementation and replace it with proper WebXR integration.

[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[midnight-dev]

Something buggy is happening when scene.logarithmicDepthBuffer is false. I noticed it on my phone which doesn't support gl_FragDepth and falls back to multifrustum. I think it's only working for the closest frustum.

@lilleyse I'm not viewing it with a headset, just using an eye trick. I don't see anything horribly wrong with the screenshot, but the basket seems a little off. Was this what caught your attention, or is the distance to the background off? I only notice an issue with the basket using just my eyes.

Also, does this multifrustum issue occur in the current pseudo VR code? If so, that problem may be outside the scope of this PR, which attempts to fix the projection angles for less eye strain.

[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[cesium-concierge]

Thanks again for your contribution @SorryNotSorryBasileus!

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[emackey]

@cesium-concierge stop

[ggetz]

@SorryNotSorryBasileus thanks for your work here, but we're going to opt to close this out. We feel our current implementation is really a stop gap solution for VR and would rather proper XR support. If you have any interest in the implantation or have further thoughts, please let us know here: #3422.