25ct wrote:

>    Thanks David,  thats great! I'll be able to have a play around with it
> now! I was really pleased with this image, and then you get to see the
> 'jaggies'! So, I  am glad that there is a part of this programme that can
> help with this.

The information is kind of scattered around if you RTFM, so I thought it'd be
better to post an example. For the longest time I was creating INI files with
the same filename as the scene and they weren't doing anything, it took me
forever to figure out you have to parse the INI!! Oh well.

If you want a full explanation of AA types and settings, read the secton
"Anti-Aliasing Options" in the docs.

--
David Fontaine     <dav### [at] faricynet>     ICQ 55354965
Please visit my website: http://www.faricy.net/~davidf/

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On Tue, 15 Aug 2000 15:11:02 +0100, 25ct wrote:
>   Hi all,
>            here is the result of my second project. I'm very pleased with
>this, especially as it is very close to the picture I had in my mind.
>   I still do not understand anti-aliasing, although it was rendered at
>512x384 AA 0.3. Can anyone enlighten me as to getting it better?

Great looking image, but it's shouting "Give Me Some AREA LIGHTS". 

From the POV documentation:

4.5.5.4   Area Lights
Area light sources occupy a finite, one- or two-dimensional area
of space. They can cast soft shadows because an object can
partially block their light.  Point sources are either totally
blocked or not blocked.  <End of quote>

Area lights slow rendering down considerably, thought I'd warn you.
The doc goes on to explain the syntax etc of area lights,  there's
also good stuff in there on AA and probably anything that you'd want
to know, there's no harm in asking here aswell as some of our regular
visitors/participants have developed knowledge that goes beyond the docs.  

-- 
Cheers
Steve              email mailto:ste### [at] zeroppsuklinuxnet

%HAV-A-NICEDAY Error not enough coffee  0 pps. 

web http://www.zeropps.uklinux.net/

or  http://start.at/zero-pps

  8:37pm  up 31 days, 19:04,  2 users,  load average: 1.04, 1.29, 1.24

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Umm. I'm tempted to write a long article here, since nobody yet have given
(no-one yet has given? argh! English is diffucult; you get it.) a thorough
explanation of AA in this thread.

Anti-aliasing is, as you know, a technique for reducing jaggies in the
image, resulting from sloped lines and the fact that the computer-screen is
a discrete medium, allowing only certain positions for your coloured dots.
(Unlike when you write with a plotter, for example.)

When you use the +axx.xx option, you turn on antialiasing. The float after
+a is the tolerance of the AA. Lower, the less tolerant. A value of 0.1 will
cause povray to trigger the AA-method for the pixel in question if the pixel
differ with 10% in colour from one of it's neighbours (to the top and left.)
A higher value will cause Povray to be more nonchalant, that is it lets
bigger differences pass.

The AA method actually shoots another ray; i.e. sample, into the scene
_between_ the two differing pixels. The resulting pixels (both the current
and the previous which differed) are then recalculated with the extra
information provided from the second sample. In that way, the image gets
smoother.

There is also an alternate method of AA; the adaptive. (Am I right here?)
Set the +am2 option, the usual +axx.xx and an additional option +rn, where n
is the recursion level. Povray will now; when it encounters two differing
pixels as before, shoot a new ray as before. But it doesn't stop here! It
does so n times, so that even the in-between "pixel" is re-sampled; giving
an even smoother image as result! Alas, the price is rendering time. Try to
model a refractive sphere over a checkered plane. If the ior is about 1.4,
you should see a "warped" version of the plane in the sphere, and it gets
typically _very_ aliased (that is you get interference patterns in the
sphere.) This effect is also visible in the horizon; where the plane meets
the sky. (!). Now, turn on antialiasing with +a0.0, +am2, +r4 and see what
happens to the render time...

In my experience, a depth (+r) higher than 2 gives almost no difference in
apperance. For high quality renders, I use +a0.1 +am2 +r3 as options. This
gives very nice results, but don't do it on test renders when you have a lot
of reflection and refraction going on in the scene!

This should be _failry_ accurate information; arrest me if I'm wrong on
something! (It's late in the evening too...) This was fun. :)

Regards,
- Simen Kvaal. (wannabe antialiasing expert...)



"25ct" <25c### [at] lineonenet> wrote in message news:39994efd@news.povray.org...
>    Hi all,
>             here is the result of my second project. I'm very pleased with
> this, especially as it is very close to the picture I had in my mind.
>    I still do not understand anti-aliasing, although it was rendered at
> 512x384 AA 0.3. Can anyone enlighten me as to getting it better?
>
>    Hope you like it.
>
>            ~Steve~
>
>
>

Post a reply to this message

Simen Kvaal wrote:

> In my experience, a depth (+r) higher than 2 gives almost no difference in
> apperance.

Try rendering a scene with a v. high frequency normal pattern. I've gone as high
as depth 5 to get good anti aliasing.

MJL

Post a reply to this message

> > In my experience, a depth (+r) higher than 2 gives almost no difference
in
> > apperance.
>
> Try rendering a scene with a v. high frequency normal pattern. I've gone
as high
> as depth 5 to get good anti aliasing.
>
> MJL
>

Sheesh! I've never run across such notorious examples! I really don't have
_that_ much experience with antialiasing; I've only done a few renderings on
a _fairly_ advanced scene and compared the differences.

A aa-depth of 5 would _drastically_ slow down render time on a complex scene
where really only a few objects actually need it. What about
object-dependent aa? You could attach a number to an object (maybe in the
finish-block) that "hints" povray on how accurate it must be rendered. When
you turn on aa, rays that hit the object in question get super-sampled
_more_ than others. I don't know, but it doesn't seen too difficult.
Speedup? Most likely.

Simen.

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In article <399a4b30@news.povray.org>, "Simen Kvaal" 
<sim### [at] remove_mestudentmatnatuiono> wrote:

> What about object-dependent aa? You could attach a number to an 
> object (maybe in the finish-block) that "hints" povray on how 
> accurate it must be rendered. When you turn on aa, rays that hit the 
> object in question get super-sampled _more_ than others. I don't 
> know, but it doesn't seen too difficult.

This should be possible for the object's texture(and of course 
reflections or refractions), but the edges would only be antialiased to 
the level specified by the object if the first ray hit the object. 
Still, it would be a useful feature.

-- 
Christopher James Huff
Personal: e-mail chr### [at] maccom, Web page http://homepage.mac.com/chrishuff/
TAG: e-mail chr### [at] tagpovrayorg, Web page http://tag.povray.org/

><>

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Thanks everyone for your help. I haven't been ignoring you, promise!
      Doh!@ me, though, for not finding where the command line was! Hehe!
(early days!)
      I've been playing around with it. It's quite inter-
esting. I haven't mastered it yet, so you can all relax! :o)
   Do I hear some sighs of relief?

     One quick question while I'm here. How can I delete
 a file from the file menu? I can't find any reference to deletion at all.
Or isn't it possible?

       Thanks again guys, ~Steve~

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On Sat, 19 Aug 2000 17:54:28 +0100, "25ct" <25c### [at] lineonenet> wrote:

>     One quick question while I'm here. How can I delete
> a file from the file menu? I can't find any reference to deletion at all.
>Or isn't it possible?

One word: RegEdit :)


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg

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"Peter Popov" <pet### [at] usanet> wrote in message
news:e6reqsoofhlp6aht5o4psk8e6amu8jg395@4ax.com...
> On Sat, 19 Aug 2000 17:54:28 +0100, "25ct" <25c### [at] lineonenet> wrote:
>
> >     One quick question while I'm here. How can I delete
> > a file from the file menu? I can't find any reference to deletion at
all.
> >Or isn't it possible?
>
> One word: RegEdit :)


   Thanks for that Peter.

        I've godit now, so I'll go and gedit!  Gedit?   :o)

         ~Steve~


>
>
> Peter Popov ICQ : 15002700
> Personal e-mail : pet### [at] usanet
> TAG      e-mail : pet### [at] tagpovrayorg

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On Sat, 26 Aug 2000 18:22:34 +0100, "25ct" <25c### [at] lineonenet> wrote:

>> One word: RegEdit :)
>
>   Thanks for that Peter.
>
>        I've godit now, so I'll go and gedit!  Gedit?   :o)

Gegege :)


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg

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