The render target used for PBR transmission wouldn’t be relevant for alpha blending (material.transparent=true). Can’t tell what type of transparency is being used here without more information though, if it’s PBR transmission then I’m not sure.
Assuming alpha blending — one option would be to use the stencil buffer and custom render order to:
- draw the model first, writing only to the stencil buffer
- draw the plane, only where the stencil buffer is already set
- draw the model again, normally
Similar to the approach suggested in this post:
Note that what this approach allows is to continue drawing the plane, but only where it lies directly behind the object, and not elsewhere. I think that’s what you intend?