Black patches on finished render

[mt_sabao]

Hi all,
well, despite all the problems I kept having with terragen (as i said before, i didn't solve nor did i try to, because i had no time) this is my final image. The background is Terragen (plus PS for color) and then models (GI, shadows) are in Cinema4D. Final comp in PS.

[Hetzen]

I really like this, shame you had problems in TG, it would be good to find out what was causing them. Did you use a series of mattes for your dust paths to generate the banks and colouring within TG? I have a feeling I might see this image at an aerospace show

[Henry Blewer]

Could the image maps for the ground be interacting with the dish objects. If they are, it could throw the geometry off for the dish objects. The trace would hit the inside faces of the dish objects, with their strange, twisted normals; causing the program to render the black patches.
It's only a hunch, but the pics mt_sabao posted reminded me of a game I used to play. The objects would go wacky if the plane of the 'dungeon' was intersected by the players character.