I use vue9 and i'm working on a project..while redering,I got some problem...

you can see,there're some kind of strange CD icon stuff on the wall(happens in the preview render,final render,etc.)...

looks it only happen on the shadow area of the wall,I can't see it on the bright area(or the ground)

the incline is just a oblique box,the basic object.It's not caused by the materials,because no matter what kind of material I use,it doesn't disappear.I use radiosity,it's not caused by it neither..the same,no matter what kind of lighting mode I use,it doesn't disappear...

OMG,any body can help me out?(I met the same problem last year,but didn't figure it out)