Is possible to get color in fragment shader from current image buffer by position? I can't find any info about it on the internet...
No, that's not possible...it would ease a lot of things, but it's not possible... :(
So, if I want this (http://www.youtube.com/watch?v=XMHC1num23I) effect (windows in rooms, which deforming image), I have to render scene to target, render depth, render final effect and somehow checking it with depth? Damn it, I want just color from image buffer :-\
edit: something like portal, which is in this tech demo ... http://www.youtube.com/watch?v=Q9MEvP_RXCY
Something like that...i don't know exactly how to do this, but you have no access to the framebuffer in the shader.
This is effect, that I mean (distortion is from texture), on photo. I'll try to do transparent glass.
(http://s17.postimage.org/uwknec9dn/Screenshot_2012_07_08_23_16_33.jpg) (http://postimage.org/image/uwknec9dn/)