Is there some kind of a problem trying to smooth heightfields that are too
high-res?

"hf no problem.jpg" looks pretty good. The heightfield it uses was rendered
in POV at a resolution of 1024x1024. "hf problem.jpg" uses a _higher_
resolution height field (4096x4096), but it gets all these ugly stripes and
interference patterns. If I get in closer I can see the landscape appears
stepped, rather than smooth. Both images are done with the same settings,
apart from the res of the hf. And yes, they both have the "smooth" command
and the hf in both cases is rendered to a 16-bit .png file :)

My hunch is that POV's smooth command doesn't compensate for the limit of
colour depth. So if you crank the resolution up high enough or have a fairly
gradual change in value then you'll get this stepping.

Does anyone know what's going wrong and how I might fix it?

Or do I just have to make do with a lower res height field?

Help? :)

--
Tek
http://www.evilsuperbrain.com

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Attachments:
Download 'hf problem.jpg' (65 KB) Download 'hf no problem.jpg' (50 KB)

Preview of image 'hf problem.jpg'

Preview of image 'hf no problem.jpg'

It looks indeed a bit strange, but i doubt it is really a matter of the
heightfield resolution, looks more like an accuracy problem of some kind.  

Things that would help:

- does it also occur without 'smooth'?
- a closeup view
- the heightfield code

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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DOH!

I can't believe how dumb I was being!!

I decided to follow your advice and try rendering it with smooth turned off,
but that was taking some time so I decided to take the opportunity to
re-read the heightfield bit of the POVray docs. I suddenly noticed the
hf_gray_16 setting, I'd swear that wasn't there before!

It's sorted now as you can see by this lovely picture.

Of course, this does mean that every heightfield I've ever done has been at
8-bit colour depth! God I feel stupid 8)

--
Tek
http://www.evilsuperbrain.com

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Attachments:
Download 'hf fixed.jpg' (49 KB)

Preview of image 'hf fixed.jpg'

Tekno Frannansa <tek### [at] evilsuperbraincom> wrote:
: Does anyone know what's going wrong and how I might fix it?

  As you already noticed by yourself, the problem is that you are using
a 256-color image to create your heighfield, which means that there are
only 256 different heights in it. When the resolution of the image is
large enough, stairs will inevitable appear.
  The solution is to use a 16-bit image for the heightfield to get 65536
different heights.

-- 
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););}    /*- Warp -*/

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