I'm wanting to use core image effects on an openGL texture.

I have found that it should be pretty easy to create a CIImage from an opengl texture by using CIImage's imageWithTexture:size:flipped:colorSpace: method.

My question is, how do I then efficiently get it back into an openGL texture after having applied the effects? Do I need to create my own FBO and render the image using CIContext's drawImage:atPoint:fromRect: method? Is this as quick and easy as I can do it?

well I pretty much answered my own question. Using the two above methods and a couple of FBOs I've got it working, and it seems fast enough. There doesn't appear to be any VRAM->RAM->VRAM stuff happening. Would still be interested to hear if there might be a faster or better way though.

Core image is pretty cool, can't believe it's taken this long for me to get around to using it!

Now to figure out how to automatically generate UI for all of the filter options...

I recall looking at this in the past and concluding that an FBO was the way to go.

Look at Core Image Fun House in /Developer/Examples for autogenerated filter UI.