the image explains it all:
No, not actually. But maybe I'm not looking closely enough or in the right spots.
Some of what I see could be uneven ground terrain. Some could be texture related. Not sure from the image which is the case at each location.
What type(s) of textures are you using? PBR by any chance?
In my latest project I am using only PBR textures. Mixing PBR and non-PBR textures can or will cause issues so I am not using any non-PBR textures.
Because PBR works by altering the height of the terrain (by a few cms or so I believe) this can cause issues where the texture intersects track and road splines. I have discovered that it can take a bit of practice, some careful texturing and/or careful terrain height adjustments under the track/road.
Its a bit of extra effort but I find that the PBR textures look a lot better than the non-PBR textures.
But, of course, this could be completely missing the point of your post.
My theories.
EDIT: This is not just a Trainz only issue. Posters here have commented that it seems to be a universal problem in all games/sims that use PBR.
