Gilles Tran wrote:

>You know you can control the amount of jitter in POV with
>Jitter_Amount=n.n / +Jn.n.  I tried for example '+A0.01 +AM2 +R6 +J10.0'.

Yes I tried that during the tests (including J10.0 to get extreme jitter and

and still got artefacts. I kept +J but to be frank I'm not sure it does
anything useful here.

>But you should notice that with +a0.0 POV-Ray supersamples every pixel
>while i am pretty sure C4D does not.

In fact, I was suprised to see POV-Ray crawl on a plain background{} with
a0.0, which doesn't make much sense. C4D slows down there a little bit only,
but it's a sky_sphere here so it's an object. With a0.0 on a real background
(like a complex texture on a plane), both applications crawl, and not only
with aa0.0...

>Concerning the origin of the discussion - from my side the result is
>about: It could be useful for speed reasons to specify different aa
>settings for different parts of the scene but specifying them on per
>object basis might often not be that useful after all.  In this scene
>for example you might want to specify +a0.0 for the sphere and its
>reflection - to do this without unnecessary slowdown it would probably
>be easiest to define an aa-map - you could generate it by rendering a
>plain color version and creating a map from it in a paint program.  This
>way you could also restrict the high aa parts even further - to only the
>poles of the sphere.

I think that the per object aa is an overall good compromise. It's very
user-friendly, and easy to test during development. I'm certainly going to
use it as a standard feature in my C4D scenes and these little tests have
been extremely helpful to understand what's going on. As I said in a
previous post, aa issues are usually texture or object-related so it's easy
to define. If you have an aa problem with an object, just improve its aa
settings until a compromise is reached.
I understand that the advantage of maps would be in situation where an
object could really use variable aa : this is the case for the sphere here
and even more for the plane (if we want a 100% correct reflection and
shadows). But then aa is adaptive after all, so it's not always such a
problem. Also, there's always the clumsy solution of using CSG to cut up the
object and giving different aa settings to its parts (something that would
be much easier in POV-Ray than in C4D btw). And the possibility of using
transparent discs or polygons in front of the camera to define aa zones (to
be tested though, I just made it up)...

Maps have also several practical drawbacks: first you can't fine tune aa
parameters that way unless you define one map by parameter (4 for POV-Ray)
or define a way to somehow link aa parameters to map colours. Second, you
won't use this in animation for obvious reasons (well, one could still
create the map automatically by generating a masked version of the scene
based on the objects - but then we're back to object-based aa). Third,
you'll have to repaint a map each time you move the camera or some of the
objects. I've been through this kind of manual editing in POV-Ray (to get
variable radiosity rather than variable aa in fact) and while feasible it's
a real pain.

G.

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