[Bf-committers] Compositing View Port Proposal

Antony Riakiotakis kalast at gmail.com
Wed Mar 28 11:24:30 CEST 2012

Not entirely true about FBOs. We already support offscreen buffers
using the GL_EXT_framebuffer_object extension. This has a way broader

I see selection was also mentioned. I did some recoding there to
support occlusion queries (I will post a diff against current trunk if
you are interested). The method worked but I couldn't extract depth
information. Since we are usually interested in only the first visible
object, I thought of implementing a 2-pass technique to first get a
list of selected objects and second, get the one on whose depth equals
the one in the one in the framebuffer. I think if we don't modify the
contents of the frambuffer, doing an occlusion query with depth test
equal is sufficient for the first click and for subsequent clicking
you can use an "always pass" depth test and queue through the objects
that passed the test. The latter can also work for alt-selecting. But
I think I can find the time I may do an implementation of this sooner
than Gsoc starts...except if there's a better implementation idea.
Some people mentioned raycasting+hierarchy based selection.

Jason, while thinking of this I also thought it would be nice to
easily override or modify an objects shader to provide for needed
state (I was thinking of modifying the fragment shader for selection
for instance, to write depth values in the framebuffer, but could be
nice for various effects).

More information about the Bf-committers mailing list