Blending Custom Stencil PostProcess Materials

I am working to create a postprocess material that only processes objects with a specific custom stencil. I then want to create instances of that postprocess for as many custom stencils as I have in my scene.

I’ve created a simple material which checks for a custom stencil value, and applies a color to objects with that custom stencil as a test:

I then create two instances of that material with different colors and stencil values:

The issue appears when I have both material instances in my scene at one time.
When both are added to my Post Process Volume, the later instance always “overrides” the previous – meaning when I only have the Pink instance, the sphere is pink. When I add the Blue instance, the Sphere
returns to normal, and the Cube is blue.

When I set the Blend Weight of the Blue postprocess to zero, the sphere goes back to pink. (It doesn’t change at any other blend weight value, only 0 or 1).

I’d like to have the effects of both postprocess materials visible at the same time.

Additional info: If I just duplicate the original material, and put the Original and Duplicate non-instance materials in my postprocess, I get the desired result! But I don’t want to create a new material for each custom stencil.

Any advice appreciated.

After much experimentation, it appears the issue is solved (i.e. both instances of the PP material are working simultaneously) by turning “Is Blendable” off in the Material settings.

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