vpos

From the looks of that error you're trying to modify the VPOS, which isn't allowed as it's a read-only input. Even if you could write to it, there wouldn't be much point as it's not used again...

The error should indicate which line is wrong, so go to that and make sure you're not changing it. If you really need to change it then make a defensive copy first...

hth
Jack

hi Jack!
I am trying to use it to access a texture. but if i put tex2D(...,vPos.xy), it also doesnt compile at runtime.

thx!
Edwin

My guess would be that you can't use swizzling on vPos. Try assigning it to a variable and using that, or just try using it without the .xy.