Large maps, weird lighting on flat surfaces.

[Bashh]

Alright new issue from the same map i posted in the models thread about phong:

Underneath the highway in my picture, there are some odd gird-like lights showing up, and I don't know why. I'm not sure if it's a problem with my texture or not, but I do realize it's because of the map size for one, but yeah.

Because of the maps being around this size as an average I need to find a way to solve this and i wondered if anyone else knew how to fix this?

 

[Mapster]

Got a more close-up picture?

 

[Shinobi]

is that a terrain patch there?

 

[undertone]

lightmaps maybe?

EDIT: nevermind, i see the lines. is that area made up of multiple brushes?

 

[Crispy]

Did you use displacement geometry to make that area?

 

[-Psy-]

Looks like the lighting is fooking up where VIS has split the faces.

 

[Crispy]

How big is that map? An idea of scale would be helpful, as Psycho could be correct (in which case there's probably a simple solution).