[Bf-committers] Multisample Z-buffer

[Reuben Martin]

Back on Saturday 20 January 2007 17:12, Joe Eagar was like:
> Reuben Martin wrote:
> > Right now the trick is to have the Z-combine node do the anti-aliasing
> > for us. In the documentation Ton writes: "Note that Z values are still
> > aliased, only 1 sample per pixel for Z is delivered to the compositor, so
> > the masks can have small artifacts."
> >
> > My question is this: would it be possible to add a rendering option so
> > that elements such as the z-buffer are rendered at a higher resolution in
> > order to provide more than 1 sample per pixel? For instace you could have
> > an option to render these elements at a scale factor of 2, 3, 4.... and
> > get 4, 9 ,16... z-buffer samples per pixel respectively. My thinking is
> > that maybe this would result in less artifacts and more precision. (Which
> > would be especially helpful when doing DOF in post) Is this thinking
> > correct?
>
> The problem here is that AA isn't just rendering pixels of an image
> 5,8,11,6 times bigger then resampling down; you actually render each
> pixel offset by a jitter value.  Really simple down sampling doesn't
> work nearly as well, especially on near-vertical lines.

Well, my thinking isn't that this would be a replacement for AA, but rather 
that a higher resolution z-buffer would provide sub-pixel precision for the 
AA masking so that when "a post-process function is used which fills in the 
jaggies with interpolated values" then it could use this sub-pixel 
information in order to create more accurate interpolation.

-Reuben