> Who cares as long as the result is free of errors?
It should be clear what it does or at least not wrong documentated imho. AA
is a very important thing, so the user should have maximal control of it.

> If you want to know how AA works, take a look at the source code.
> It is not like everything has changed in 3.5 :-)
Does this mean, AA hasn't changed and I can use the 3.1 source?

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>   You are welcome to suggest an algorithm for that.

I've had a very hard time finding any information on alternate algorithms.
Most of the ones I found sound like what POV does. I brought it up, because
for example, 3d studio max has about a dozen AA methods. Most of them are
redundant or crappy, but there are one of two which give a nice effect
overall to the rendering. I wonder if the reason I can't find anything is
because it isn't free information? :P

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>   You are welcome to suggest an algorithm for that.

By the way... have you looked at the AA methods that the GeForce 4 uses?
Maybe you could find something useful there. Check out the recent review on
AnandTech.com.

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Ron Parker <ron### [at] povrayorg> wrote:
:>   Does it work for reflections/refractions as well?-)

: No.  But then, those are harder for the existing AA methods too.

  How so?

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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In article <3c6ab2c5@news.povray.org>,
 "Thorsten Froehlich" <tho### [at] trfde> wrote:

> Won't work well:  Remember that the ray is infinitely thin, so you will have
> some spacing between rays.  Of course, you can make the sampling so small that
> is scratches floating-point precision, but I doubt this would really improve
> quality.

The point of using an X pattern would be to make it more likely to find 
a thin object while using fewer samples. I know it wouldn't be perfect, 
but it might work faster than sampling in a grid.


> What can be done with every object with a known surface is to find a few
> points on the surface and then start sampling from there (so doing AA with
> superpixels first).  It would work for all objects with a single surface or a
> number of parts/surfaces assuming you can supply one point for each of them.

So, if a pixel hit an object but an adjacent one didn't, supersample the 
surrounding ones to make sure they didn't hit it, and supersample 
outwards until you run out of pixels that hit the object?

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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In article <3c6ab883@news.povray.org>, "Tony[B]" <ben### [at] catholicorg> 
wrote:

> By the way... have you looked at the AA methods that the GeForce 4 uses?
> Maybe you could find something useful there. Check out the recent review on
> AnandTech.com

That's scanline rendering...a completely different situation from 
raytracing.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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On 13 Feb 2002 14:04:51 -0500, Warp wrote:
> Ron Parker <ron### [at] povrayorg> wrote:
>:>   Does it work for reflections/refractions as well?-)
> 
>: No.  But then, those are harder for the existing AA methods too.
> 
>   How so?

Supersampling over a single screen pixel isn't enough to resolve fine details 
if they're magnified by reflections or refractions.  That's one of the 
problems that the Tracing Ray Differentials paper was trying to solve.

--
#macro R(L P)sphere{L __}cylinder{L P __}#end#macro P(_1)union{R(z+_ z)R(-z _-z)
R(_-z*3_+z)torus{1__ clipped_by{plane{_ 0}}}translate z+_1}#end#macro S(_)9-(_1-
_)*(_1-_)#end#macro Z(_1 _ __)union{P(_)P(-_)R(y-z-1_)translate.1*_1-y*8pigment{
rgb<S(7)S(5)S(3)>}}#if(_1)Z(_1-__,_,__)#end#end Z(10x*-2,.2)camera{rotate x*90}

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"Felix Wiemann" <Fel### [at] gmxnet> wrote in message
news:3c6a935b@news.povray.org...
> Hi,
> when I use anti-aliasing and treshold 0.0 (+A0.0) with an empty (black)
> scene, every pixel is super-sampled. The doc says every pixel which
differs
> *more* than threshold is sampled, but that's not true.

Good point.  As others pointed out, it should say "at least".

> Try +A0.001: No pixel
> is sampled anymore!

Why is this such a surprise?  You're asking for a difference of 0.001, but
all of the pixels are exactly the same (difference = 0), so they _shouldn't_
be supersampled.  This is the expected behavior.

...Chambers

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"Warp" <war### [at] tagpovrayorg> wrote in message
news:3c6aa79b@news.povray.org...
> Tony[B] <ben### [at] catholicorg> wrote:
> : Has the Team ever considered adding more AA methods? It'd be nice if you
> : found one that handled very thin lines a little better.
>
>   You are welcome to suggest an algorithm for that.

Simplified version (for the final viewing plane):
Check the object's bounding hierarchy for the maximum and minimum elevations
above the horizon, as well as the rotations from center.  Plot as a box.
AFAIK, this is the method used for visa buffer.
If a pixel is within the box, but it's neighbor is not, supersample between
them.  If a box lies entirely between the two pixels, supersample them.
If both pixels are within the box, one hits the object and the other does
not, supersample between them.

The current sampling method is color based, and works to ensure all portions
of the screen look nice.  This method, being intersection based, deals with
edges / small objects very nicely, but will not address aliased textures.

BTW, this is off the top of my head, I don't know if it is really practical
or if it has even been previously published (just seems to make sense to
me).

...Chambers

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"Warp" <war### [at] tagpovrayorg> wrote in message
news:3c6ab534@news.povray.org...
> Ron Parker <ron### [at] povrayorg> wrote:
> : Actually, there is a way: the vista buffer.
>
>   Does it work for reflections/refractions as well?-)

Does the current method?  I was under the impression that supersampling was
done only on the rays shot from the view plane, and not on reflection /
refracted rays.

...Chambers

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