On 07/06/2014 10:05 PM, Krzysztof Kosiński wrote:
... We could do three things a) put in some logic to arbitrarily stop rendering an effect when the dependent area crosses some threshold b) use stacked box blur instead of true Gaussian blur (though I doubt it would be faster) c) speed up the existing Gaussian blur implementation - it shouldn't be that slow
The stacked box blur would be unacceptably wrong for export purposes (in contrast to what seems to be popular belief, you most definitely can see the difference between most of the simple approximations and a true Gaussian blur), but for viewing it might not be the worst possible idea.
As for speeding up the existing implementation, the current algorithms is probably /the/ fastest high quality(!) implementation around (at the time I had a good look around to see what was there, and most programs either used bad approximations or a simple convolution...). Having said that, it turns out that this particular algorithm, though superfast in theory (something like 7 flops per pixel), does need quite a bit of tweaks to make it behave properly, affecting its speed quite badly (and also making use of SSE and the like a little harder).
So while I believe it might be hard to speed up the current implementation significantly, there is definitely room for a faster low quality algorithm that could be used for viewing purposes.
We could of course also use a GPU or whatever, but that's also not entirely trivial.
(BTW, I should still have some attempts at replacing the current algorithm lying around, and I have a few weeks off soon, so perhaps it's time to dust that work off...)