So in your setup, the red surface and the white surface are two separate 3D Tilesets, right? And they almost have the right outcome, but they are clipped with a slight offset from each other?
I think this slight offset is coming from this line:
modelMatrix: Matrix4.inverse(tileset._initialClippingPlanesOriginMatrix,
new Matrix4())
});
It almost looks like they have a different origin. Does each clipping plane use the respective tileset’s _initialClippingPlanesOriginMatrix ? I believe that should be the right configuration. If so, what happens if they share the same model matrix?