How to render Depth (Cull Front) in XR (VR) mode with Custom Pass

Unity Engine
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1

Hi!
I created a simple command for rendering custom depth (with front culling, when we got back polygons) in Custom pass.
I do it with this code:

CoreUtils.SetRenderTarget(cmdList, Depth_Back_Buffer, ClearFlag.All);
CustomPassUtils.DrawRenderers(ctx, CustomLayer, RenderQueueType.AllOpaque, CustomVFmaterial, 0, overrideRenderState: new RenderStateBlock(RenderStateMask.Depth){depthState = new DepthState(true, CompareFunction.LessEqual)});

And very simple VF shader pass:

Blend  Off
ZWrite Off
ZTest LEqual
Cull Front

PackedVaryingsType Vert(AttributesMesh inputMesh)
            {
                VaryingsType varyingsType;
               
                //VR REQUIREMENT
                UNITY_SETUP_INSTANCE_ID(inputMesh);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(varyingsType);
               
                varyingsType.vmesh = VertMesh(inputMesh);
                return PackVaryingsType(varyingsType);
            }

            float4 Frag(PackedVaryingsToPS packedInput) : SV_Target
            {   
                //VR REQUIREMENT
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(packedInput);
                return 0;
            }

Everything work is okay, when I’m trying to use it in standart mode (without VR mock), I got texture (one slice ) and correct depth with Front culling (example with standart Cube in attached files “Not XR”)
But if I want to use XR mode (with MockHMD in Single-Pass Instanced rendering mode), it returned depth (in two eyes) with Back culling mode (example with standart Cube in attached files “XR”, first slice - left eye, and second slice have a correct camera offset but anyway Back culling depth).
Why is it happening and how can I solve it? (Unity 2022.2.3f1, HDRP 14.0.5, XR Plugin Management 4.2.1)
If you needed to reproduce it, I can create a simple Unitypackage.
Thanks in advance!

8819731--1200505--Not XR.png
8819731--1200505--Not XR.png1440×941 43.6 KB

8819731--1200508--XR.png
8819731--1200508--XR.png892×1122 40.1 KB

2

Hello,

In your shader code, you have the ZWrite set to Off. If you try to write the depth with this setup it will not work.
Other than that I don’t see any problem or issue that could happen only in XR mode

3

Thanks!
ZWrite doesn’t affect the result in any way.
But when I created a test scene for you, I created a new shader and got the error (I have never seen it before):

Shader error in 'Custom/VFshader': invalid subscript 'stereoTargetEyeIndexAsRTArrayIdx' at line 46 (on d3d11)

Compiling Subshader: 0, Pass: FrontFaceCullPass, Vertex program with STEREO_INSTANCING_ON
Platform defines: SHADER_API_DESKTOP UNITY_ENABLE_DETAIL_NORMALMAP UNITY_ENABLE_REFLECTION_BUFFERS UNITY_LIGHTMAP_FULL_HDR UNITY_LIGHT_PROBE_PROXY_VOLUME UNITY_PBS_USE_BRDF1 UNITY_SPECCUBE_BLENDING UNITY_SPECCUBE_BOX_PROJECTION UNITY_USE_DITHER_MASK_FOR_ALPHABLENDED_SHADOWS
Disabled keywords: DOTS_INSTANCING_ON INSTANCING_ON SHADER_API_GLES30 UNITY_ASTC_NORMALMAP_ENCODING UNITY_COLORSPACE_GAMMA UNITY_FRAMEBUFFER_FETCH_AVAILABLE UNITY_HALF_PRECISION_FRAGMENT_SHADER_REGISTERS UNITY_HARDWARE_TIER1 UNITY_HARDWARE_TIER2 UNITY_HARDWARE_TIER3 UNITY_LIGHTMAP_DLDR_ENCODING UNITY_LIGHTMAP_RGBM_ENCODING UNITY_METAL_SHADOWS_USE_POINT_FILTERING UNITY_NO_DXT5nm UNITY_NO_FULL_STANDARD_SHADER UNITY_NO_SCREENSPACE_SHADOWS UNITY_PBS_USE_BRDF2 UNITY_PBS_USE_BRDF3 UNITY_PRETRANSFORM_TO_DISPLAY_ORIENTATION UNITY_UNIFIED_SHADER_PRECISION_MODEL UNITY_VIRTUAL_TEXTURING

I tried to comment this line:

UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(varyingsType);

And finally! Everything works now!

Can you explain please why this happened so that in the future I will know the nuances.

  1. Why everything works with ZWrite Off parameter?
  2. Why I don’t need UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO macro?
    Thanks in advance!
4

Hard to say without seeing the context of the effect, but as far as I know it shouldn’t have worked.

This is for VR support, if you don’t plan on supporting VR then it’s fine to remove it.