This is getting so complex…
Let’s see…,
About the isolation of the displacement @PatrickRyan is mentioning, I tried to do it as I usually do in offline rendering pipelines…, just by forcing the textures to show in a range of the UVs only. So in U direction, the texture is used in the 100% of the range, but for V it is used just in the 90%, leaving the last 10% blank.
The UVs of the object are designed precisely for that purpose, so it should work right away. Please see here:
You can see the displacement is not affecting that 10% of the regular plane. It should work with the final OBJ of course. I don’t know where the problem is.
About the vertices not being welded, my solution would be to have two set of vertices at the very same location, so one row would have displacement and the others would’t.