Using painted vertex color creates artifacts on lods

I made a custom material in which I offset and rotate the UV coordinates by the objects location and red vertex paint channel to break up repetition.

This works great so long as I only use the red vertex paint that is baked into the model or handpainted per instance.

When I start painting blue or green vertex colors, !that are not actually even hoocked up to anything inside the material yet! the model gets stretching artifacts on it´s lods, as if the red vertex channel is overwritten on the lods, which leads to uneven offset of the UVs on some polygons.


I want to use the green channel to add moss and the blue to add age, so it would be great if anyone could tell me what exactly is happening to the red vertex paint on the lods and why it changes when I explicitly paint only on the green or blue channel.

Some more details:

The strechting only appears when the red channel has multiple shades of red in it. As you can see on the screenshots, I use the red channel to give identical building blocks a different offset, so one shade of red covers one whole element.

I belive that when I start overwriting the baked in vertex colors with handpainted vertex colors, that “corrupts” the vertex color projection of the lods. How can I fix this? Is there a way to force the instance of the mesh that I painted on to update its projection for the lods? And why would painting on the blue channel change the way the red channel is projected down to the lods???

When I check “Allow paint on all LODs” in the painting menu, the issue is also not happening, but I have to handpaint all 4 detail levels, which is too much work to be a good work around. Howerver, this also points towards an issue with the way Vertex Paint that was handpainted on an instance is projected onto the lods.

I narrowed the issue down to how vertex paint that was handpainted is projected by using average values. But I don´t know how to force ue4 to use the hard projection method on handpainted meshes. Any idea?