View Full Version : Best guess, two options for combining textures...

07-13-2011, 12:42 AM
If you had a fbo with 3 fullscreen render textures attached, with an image in two of them, which would be the better option to combine them, performance wise. Im thinking 2 would win in flexibility and performance.

1) Set one of them as the target and fullscreen blend (in place) the other over top.
2) Set the third as the target, combine the other two using a simple shader.

The result of combining will be used again for other work. Not need atm to preserve the two original images.

I havent done either yet, just want some feedback based on others experience.

07-13-2011, 12:52 AM
In my deferred engine I ended up running a shader purely becuase of the extra flexibility it offered (in other words I could something else which blend could not).
Blending is carried out by dedicated h/w so I'd expect it to be more optimal.
Having said that, I hardly think this is going to the frame limiting step for your entire application, so on that basis I don't think its going to matter either way IMHO.

07-13-2011, 09:48 AM
I'd also vote 1 for performance but would prefer 2 for flexibility; if it's fast enough then it's fast enough and I'd take a slight drop as an acceptable tradeoff.