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From: tahoma
Subject: mipmapping
Date: 11 May 2005 14:06:07
Message: <opsqmhwj1tbx3aaw@leningrad>
When using image_maps i could not manage to get really nice visual resul
ts  

because of high sampling frequencies.
Is there a way to specify mipmaps in povray or can povray do it by itsel
f?  

The only interpolation schemes i found are 'bilinear' and 'normalized  

distance'.
My realtime images look still better than the ones rendered with povray.

I just started with it, so i still probably miss a lot of things.

Regards,
Jan


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From: Tim Nikias
Subject: Re: mipmapping
Date: 11 May 2005 14:22:11
Message: <42824d53$1@news.povray.org>
POV-Ray doesn't support mipmaps. What you normally do to avoid aliasing is
use (*tadaa*) antialiasing.

There are two methods in POV-Ray, I tend to use the adaptive one to make use
of higher but more controlled sampling. Aside of that, there'll sure be a
way to script your own kind of mipmapping (switching the texture dependant
on distance to the camera, for example), but I don't have a script "off the
shelf" for that.

That aside, once you switch on arealights, radiosity, reflections,
refractions and media, I doubt that your realtime images look better (or
that they're even realtime then). ;-P

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>


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From: tahoma
Subject: Re: mipmapping
Date: 11 May 2005 14:29:35
Message: <opsqmizllqx5erxw@leningrad>
> POV-Ray doesn't support mipmaps. What you normally do to avoid aliasin
g  

> is
> use (*tadaa*) antialiasing.
>
> There are two methods in POV-Ray, I tend to use the adaptive one to ma
ke  

> use
> of higher but more controlled sampling. Aside of that, there'll sure b
e a
> way to script your own kind of mipmapping (switching the texture  

> dependant
> on distance to the camera, for example), but I don't have a script "of
f  

> the
> shelf" for that.
>
> That aside, once you switch on arealights, radiosity, reflections,
> refractions and media, I doubt that your realtime images look better (
or
> that they're even realtime then). ;-P

You are right, of course :)
I described my current state, when i tried to export my realtime scenes 
 

into
povray without doing fancy things you mentioned.

What is the other antialising method? If you could post some settings
i can play with it would be great.


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From: Christoph Hormann
Subject: Re: mipmapping
Date: 11 May 2005 14:30:02
Message: <d5tiqg$8pd$1@chho.imagico.de>
tahoma wrote:
> When using image_maps i could not manage to get really nice visual 
> results  because of high sampling frequencies.
> Is there a way to specify mipmaps in povray or can povray do it by 
> itself?  The only interpolation schemes i found are 'bilinear' and 
> 'normalized  distance'.

Sorry but the fact you write this shows that you have absolutely no idea 
how raytracing works and what mip-mapping is.

I don't want to appear brusk but you should think about things and 
inform yourself a bit better before posting something like this.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 03 May. 2005 _____./\/^>_*_<^\/\.______


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From: tahoma
Subject: Re: mipmapping
Date: 11 May 2005 14:40:22
Message: <opsqmjhjlqx5erxw@leningrad>
>> When using image_maps i could not manage to get really nice visual  

>> results  because of high sampling frequencies.
>> Is there a way to specify mipmaps in povray or can povray do it by  

>> itself?  The only interpolation schemes i found are 'bilinear' and  

>> 'normalized  distance'.
>
> Sorry but the fact you write this shows that you have absolutely no id
ea  

> how raytracing works and what mip-mapping is.

Exactly what does imply your opinion? Because i did ask for a feature
that seems to be nonsense in you eyes?

> I don't want to appear brusk but you should think about things and  

> inform yourself a bit better before posting something like this.

You do not appear brusk. I know that i just started to understand
raytracing (especially povray). That is a long way.
I read documentations and so on. Nevertheless it is
useful to share one's thoughts with others even when they appear to be
dumb. Thats how learning works in my opinion. If you dont want to answer

to my questions, no problem. I know i am an 'alien' at this place, but
to discourage me is maybe the wrong way.


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From: Warp
Subject: Re: mipmapping
Date: 11 May 2005 15:01:47
Message: <4282569b@news.povray.org>
tahoma <tah### [at] gmxde> wrote:
> Is there a way to specify mipmaps in povray or can povray do it by itself?  

  You probably don't want mipmapping alone, because all by itself it's
pretty useless (well, not useless, but it causes a very visible abrupt
change at the places where the mipmap level changes). What you want
is trilinear interpolation.
  Unfortunately POV-Ray does not support that. There are a couple of
problems implementing trilinear interpolation in a raytracer. They can
probably be solved, but it's not as trivial as in a scanline renderer.

-- 
                                                          - Warp


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From: Warp
Subject: Re: mipmapping
Date: 11 May 2005 15:03:21
Message: <428256f9@news.povray.org>
Tim Nikias <JUSTTHELOWERCASE:timISNOTnikias(at)gmx.netWARE> wrote:
> POV-Ray doesn't support mipmaps. What you normally do to avoid aliasing is
> use (*tadaa*) antialiasing.

  Antialiasing doesn't help too much when there are dozens of imagemap
pixels in one result image pixel. It helps a bit, but does not give
such a good result as trilinear interpolation.

-- 
                                                          - Warp


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From: Warp
Subject: Re: mipmapping
Date: 11 May 2005 15:04:42
Message: <4282574a@news.povray.org>
Christoph Hormann <chr### [at] gmxde> wrote:
> Sorry but the fact you write this shows that you have absolutely no idea 
> how raytracing works and what mip-mapping is.

  How so?

  I don't see why mipmapping, and better yet trilinear interpolation
of image maps could not be implemented in a raytracer. There are a
couple of twists, but they can be probably solved.

-- 
                                                          - Warp


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From: Tim Nikias
Subject: Re: mipmapping
Date: 11 May 2005 15:10:53
Message: <428258bd@news.povray.org>
> What is the other antialising method? If you could post some
> settings i can play with it would be great.

Both settings can be set via the commandline. If you're using POV-Ray for
Windows, there's a small box on the top where you can enter options. To
switch antialiasing on, add "+AM1" or "+AM2" (without the quotation marks)
into the box. That'll select antialiasing method 1 or 2 (2 is the adaptive
one). +A0.3 will set that the next samples are shot when the current ones
differ in color by that amount (I think the difference from black to white
is 3, 1 for each channel of rgb). You can lose lower values (+A0.01) for
more detailed settings, but it will only shoot up till the maximum amount of
samples you set, which are set with +R2. The value after R refers to the
level of sampling, not the actual amount of samples. On antialiasing method
1, +R2 sets 4 samples, whereas method 2 has 25. On level 5, method 1 has 25
samples, method 2 has 1089.

You might want to read section 3.1.2.8.4 of the docs (or just search for
"antialias") for more detailed information.

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>


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From: tahoma
Subject: Re: mipmapping
Date: 11 May 2005 15:13:19
Message: <opsqmk0kjpx5erxw@leningrad>
>> Is there a way to specify mipmaps in povray or can povray do it by  

>> itself?
>
>   You probably don't want mipmapping alone, because all by itself it's

> pretty useless (well, not useless, but it causes a very visible abrupt

> change at the places where the mipmap level changes). What you want
> is trilinear interpolation.
>   Unfortunately POV-Ray does not support that. There are a couple of
> problems implementing trilinear interpolation in a raytracer. They can

> probably be solved, but it's not as trivial as in a scanline renderer.


Trilinear filtering is what i asked for. Because of the depedency of
mipmapping i just mentioned this one. If povray would support mipmapping

then trilinear filtering would be naturally there i think.


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