Splat Painting not Supported by Shader

Error: Splat Painting not Supported by Shader

This warning appears when the mesh's assigned material uses a shader that does not read UV2/UV3 splat weight channels. OptiDraw can write the data to the mesh, but if the shader ignores it, the painted blend weights have no visual effect.

Quickest Fix — Use a Template Shader

1. 1Select the material assigned to your mesh
2. 2Change the shader to OptiDraw/SplatBlend (or the URP/HDRP variant)
3. 3Assign your 4 texture sets in the material Inspector
4. 4Splat Paint will now produce visible results immediately

Fix for Custom Shaders — Shader Graph

If you need to keep a custom shader, add UV2 sampling to it:

1. 1Open your Shader Graph
2. 2Add a UV node, set channel to UV2
3. 3Split the RGBA output: R = Layer 1 weight, G = Layer 2 weight, B = Layer 3 weight, A = Layer 4 weight
4. 4Use each weight as a Lerp factor between your texture samples
5. 5Repeat with a UV3 node for layers 3 and 4 if you need more than 2 blend layers