[Bf-committers] Peach developer wishlist

[Matt Ebb]

On 08/09/2007, at 5:24 AM, Alfredo de Greef wrote:

> (btw, about the HDR aliasing problem, as I mentioned
> to broken some time ago, the way I dealt with that in
> yafray is simply by clamping/tone mapping *before*
> anti-aliasing, not afterwards. Of course, as broken
> then remarked, I forgot about the compositor. If the
> compositor had full access to all samples that would
> solve that problem, but the data would then probably
> be quite unmanagable, at least in its current form)

But then I also had an idea too, that you could clamp/tone map before  
AA by default, but also provide the un-clamped (or just the  
overbright values) as a render pass. So in situations where you need  
the HDR colours, they are available to use, and in situations where  
you don't, you don't need to incur any memory overhead. If I recall  
correctly, the RPF format provides this as one of its render pass  
slots[1] so it's probably done in other apps too.

Another idea is to a) clamp the pixels before AA, but then b) go back  
over the final AAed image, and for each pixel that is clipped at  
1.0,1.0,1.0, fill in the original HDR values. This would mean that  
the transition from light to dark is within 0.0-1.0 but you still get  
the overbright values to do stuff with later, like blurring for  
example. Check this comp to see a bit of an example of what I mean  
here: http://mke3.net/rt/aa_hdr.blend.zip

Of course there's lots of clever people on the case to solve it, but  
the rendering to 4k idea would scare me a bit if I was working with  
it.. Rendering to 4K means a lot of memory used, if only just for the  
render buffers. At work (on Windows of course which isn't too good at  
this) I've had huge problems rendering 5k+ images for print with  
multiple render layers/passes, if only just because of the amount of  
memory that needs to be allocated at the start and comp stage of the  
render, when using lots of passes/layers. I wouldn't be looking  
forward to comping 4k images either, it's slow enough right now at  
HD... Doing the render 4k/scale down method also seems inefficient -  
in effect, it's like having full oversampling switched on for every  
pixel in the frame, whether it needs it or not, no?

cheers

Matt



[1] http://www.fxguide.com/fxtips-114.html

------------------------------------------
Matt Ebb . matt at mke3.net . http://mke3.net



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