koobas.hobune.stream
Overwrite View matrix and projection matrix in VR
I am trying to make portals (Like from the game portal). With the LWRP. I first did it for non VR, where I had RendererFeature That would draw the scene again, but with a different View/projection matrix. I set those matrices with: CommandBuffer.SetViewProjectionMatrices(...);. This works perfectly, but when I enabled VR and tested that. Then the projection/view matrices are just the normal ones from the camera.
Does anyone know a technique I can use to overwrite them like I did with the non-vr version?
Well it should be clear that to get the portals rendered properly you need to render your portals twice for each eye seperately since each eye has a seperate camera and therefore seperate virtual cameras for a single portal. I haven't really played around with VR and I don't have any hardware for it. So I can not help you any further at the moment.
For future reference, I was using Unity 2019.2.6f1.
I saw in the Unity CG documentation that some .cginc files were automatically included, one of them was UnityShaderVariables.cginc. In that I found that unity_MatrixV was redefined as unity_StereoMatrixV[]:
#if defined(USING_STEREO_MATRICES)
#define glstate_matrix_projection unity_StereoMatrixP[unity_StereoEyeIndex]
#define unity_MatrixV unity_StereoMatrixV[unity_StereoEyeIndex]
#define unity_MatrixInvV unity_StereoMatrixInvV[unity_StereoEyeIndex]
#define unity_MatrixVP unity_StereoMatrixVP[unity_StereoEyeIndex]
#define unity_CameraProjection unity_StereoCameraProjection[unity_StereoEyeIndex]
#define unity_CameraInvProjection unity_StereoCameraInvProjection[unity_StereoEyeIndex]
#define unity_WorldToCamera unity_StereoWorldToCamera[unity_StereoEyeIndex]
#define unity_CameraToWorld unity_StereoCameraToWorld[unity_StereoEyeIndex]
#define _WorldSpaceCameraPos unity_StereoWorldSpaceCameraPos[unity_StereoEyeIndex]
#endif
Then lower in the file it showed where those variables were actually stored:
#if defined(USING_STEREO_MATRICES)
GLOBAL_CBUFFER_START(UnityStereoGlobals)
float4x4 unity_StereoMatrixP[2];
float4x4 unity_StereoMatrixV[2];
float4x4 unity_StereoMatrixInvV[2];
float4x4 unity_StereoMatrixVP[2];
float4x4 unity_StereoCameraProjection[2];
float4x4 unity_StereoCameraInvProjection[2];
float4x4 unity_StereoWorldToCamera[2];
float4x4 unity_StereoCameraToWorld[2];
float3 unity_StereoWorldSpaceCameraPos[2];
float4 unity_StereoScaleOffset[2];
GLOBAL_CBUFFER_END
#endif
Then I tried to use CommandBuffer.SetGlobalMatrixArray(...) to set the array but that would not work for some reason.
The only way I found out how to override the V/P matrices for VR was to use CommandBuffer.SetGlobalConstantBuffer() for UnityStereoGlobals. This however meant that I needed to manage all the matrices. I will put down what I know at this point:
For some reason Unity stores duplicates of the matrices. For example, unity_StereoMatrixP is the same as unity_StereoCameraProjection.
I believe that the Stereo projection/view matrices should be obtainable with Camera.GetStereoViewMatrix(eye) and Camera.GetStereoProjectionMatrix(eye).
The unity_StereoWorldSpaceCameraPos is as you would expect the Camera.transform.position.
And the unity_StereoScaleOffset is split up in 2 parts. 'xy' is the scale and 'zw' is the offset. This is different for each eye. I believe this is used to transform the UV's to be the correct uvs for the render target.
