blotchy render on some surfaces

[bradpski]

hey all, i have imported a large site model from another source and it was a messy model made up from different smaller models!! i have cleaned it up to where i need it to be, however when i render it (with all materials replaced with a default grey vray mat) there are a bunch of buildings that turn out very blotchy and/or very dark, i think that it is becuase there is another surface very close to the top face in these instances, but as they are solid blocks, i cannot edit them, is there a way to solve this without re-moddeling them?? thanks brad[ATTACH]16611[/ATTACH]

[JamesTaylor]

its looks to me as if, like you say, there is duplicate geometry in the same place..... i would check that 1st, otherwise i think the geometry is corrupt in someway and would suggest remodeling the blocks.... i would imagine this is only a 5min job and should solve your problem.

[kippu]

increasing the secondary ray bias a little also helps... its in the global switches panel

[dynaman]

yep - set the secondary ray bias to 0.001. this has always worked for me.

 

PS. that's a pretty freakin cool model

[danatgia]

Ive had this several times. I think James is right and you have duplicate geometry. A quick tidy-up should sort it

[Tim Saunders]

I in fact garrentee there are coplanar faces. if you can't edit it, maybe there is another way to export and/or omport the model so you have a way to edit/remove the unwanted geometry. This is reason number 1 of 50 that I can't stand rendering with BIMs.