I'm having a hard time working out your sun angle. The lighting and shading of those rocks looks a bit wonky, to me.
It looks like the two rock formations are casting shadows towards the buildings but those shadows aren't being applied to the displacements in the map area, or at least the shading is different due to lightmaps and the fact the displacements are not really connected, as they are in different parts of the map. If they were all together in the same place (the skybox or the map), the shading would be smoother.
Q. Do you get this after doing a 'final' VRAD compile?
Q. Are you using the -noskyboxrecurse argument with VRAD?
Q. Did you decrease the lightmap resolutions of your skybox displacements?
Things to try:
- Move the displacements beneath your buildings at the bottom of the image in to the skybox. They will show up where they are now, but they should be evenly shaded if they are scaled down and bolted on to the others. You will need to build some collision brushes in the real world in case players fall down there, or keep duplicates of the originals and find some transparent texture that doesn't cause compile errors.
- Increase skybox displacement lightmap resolution to hopefully brighten up the shading towards the end.
- Mitigate the difference using phantom lights, though this might be difficult if you compile in HDR. It will certainly be a pain in the arse.
- Try Block Light brushes at various heights and pitches.
It looks very nice besides!