To access scene vertex data, implement a custom render pass that renders the scene with a specific override material into a global texture. The standard Vertex Color node in a full-screen shader graph is bound to the mesh used for the blit operation, which is typically a single quad covering the camera view.

1. Create a Shader that outputs IN.vertexColor to the fragment color.
2. Create a ScriptableRenderPass that uses DrawingSettings with a FilteringSettings mask.
3. Configure the pass to render into a custom RenderTexture.
4. Set that RenderTexture as a global shader property using cmd.SetGlobalTexture.
5. In your full-screen shader graph, replace the Vertex Color node with a Sample Texture 2D node referencing the global RenderTexture name.

Additional Tips:

• Use RenderPassEvent.AfterRenderingOpaques to ensure all static geometry has been processed before sampling.
• Ensure the RenderTexture format supports the precision required for your vertex data (e.g., GraphicsFormat.R8G8B8A8_SRGB).
• Utilize ShaderTagId in your DrawingSettings to only include objects with specific tags in the vertex color pass.