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[XR SDK] Shadow is displayed inconsistently between right and left eye when Single Pass instancing rendering mode is used

Package: XR Management


Reproduction steps:
1. Open the attached project ("")
2. Open the "ShadowBug" scene
3. Enter Play mode

Expected result: Shadow in both eyes are displayed aligned
Actual result: Shadow in the right eye isn't aligned (see "q88PM5ioac.mp4" video)

Reproducible with: XR SDK 4.0.5 (2019.4.27f1, 2020.3.10f1, 2021.1.9f1, 2021.2.0a18)
Not reproducible with: 2018.4.35f1 (XR SDK not available)

- Oculus Rift S
- MockHMD

  1. Resolution Note:

    The fragment shader needs to have the following macro (at the beginning of the function) to be able to sample the right shadowmap slice for the second eye :


    UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO tells the GPU which eye in the texture array it should render to, based on the value of unity_StereoEyeIndex. This macro also transfers the value of unity_StereoEyeIndex from the vertex shader so that it will be accessible in the fragment shader only if UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX is called in the fragment shader frag method.

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