OpenGL render to texture - resize rtt-texture

Question

I'm just pulling my hair out an can't find a hint: my app resizes its RTT texture when needed via glTexImage2d with the new texture resolution.

When upsizing it all looks good. When downsizing, it looks like the TexCoord mapping of [1.0;1.0] maps to [oldRes.width; oldRes.height]. I'm sure I'm missing something vital, but cannot find it right now. Any ideas?

Answer 1

EDIT: oops, that wasn't it, also. My State Cache simply didn't enable the correct texturing unit on bind, when that texture already was bound (this fix also fixed different other problems).

I just found it - just too simple: obviously (I'm on NVidia) the texturing unit our RTT texture is bound to needs to be reinitialized after resize (NOT ON INITIAL SIZING). Unbinding the texture and rebinding it when needed again did the job.

P.S.: I'm working on a State-Cache that uses all available texturing units - that's why this popped up: the texture was never unbound as my examples use much less textures than there are units... (so no texture gets unbound unless deleted).