Meta Quest Optimization 2026-05-26 Updated

Measures to take when rendering is broken in only one eye with a Single Pass Instanced compatible shader for VR (Meta Quest)

Difficulty Advanced

Unity Version Unity 2022.3 LTS / Unity 6 対応

Target Audience VR game developer, shader programmer, TA

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Symptom

When I enabled Single Pass Instanced (or Multiview) drawing for Meta Quest, etc., objects to which I applied my own Shader Graph effects or custom HLSL shaders looked normal to the left eye, but were not displayed at all to the right eye, or the drawing positions of the left and right eyes were shifted, resulting in strange stereoscopic vision.

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Root Cause

The cause is that in the custom shader's vertex shader processing, the "stereo instance ID" processing and coordinate system conversion macro required to draw the two left and right viewports of VR and the coordinate system conversion macro are not written correctly, so only the coordinates for the left eye are calculated on the GPU.

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Solution

In handwritten HLSL, add macros for stereo indexing to the vertex input (Attributes) and output (V2F) structures, and execute the initialization macro at the beginning of the vertex shader. For Shader Graph, follow the code generator through a standard platform-compatible transformation node.

This is a workaround for a bug where self-made shaders are not drawn only on the right eye when SPI is enabled in VR. This is a countermeasure for a bug where self-made shaders are not drawn only on the right eye when SPI is enabled in VR.

Specific solution

Apply the following macro to the structure of the hand-drawn shader (HLSL) and the beginning of the vertex shader.

struct Attributes
{
    float4 positionOS   : POSITION;
    UNITY_VERTEX_INPUT_INSTANCE_ID // ➔ Add this! 
};

Varyings vert(Attributes input)
{
 Varyings output = (Varyings)0;
 UNITY_SETUP_INSTANCE_ID(input); // ➔ Add this! 
 // ...coordinate transformation...
 return output;
}