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Is there a way of finding the highest parts of a hf. I don't just want
everything above a certain height but the top of every bump. Hope this is
clear.
Hope someone can help.
Mick
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Mick Hazelgrove wrote:
>
> Is there a way of finding the highest parts of a hf. I don't just want
> everything above a certain height but the top of every bump.
A basic method in MegaPOV would be to get a grid of height values (using trace)
and start comparing: if a point is higher than all 8 points around it (or 5
points at the edges, or 3 points in the corner) it is the top of a bump.
Of course it's a bit more complicated if you want more control, e.g. only
consider convexities above a certain scale as "bumps".
--
Margus Ramst
Personal e-mail: mar### [at] peak eduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
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Margus Ramst wrote:
>
[...]
> A basic method in MegaPOV would be to get a grid of height values (using trace)
> and start comparing: if a point is higher than all 8 points around it (or 5
> points at the edges, or 3 points in the corner) it is the top of a bump.
> Of course it's a bit more complicated if you want more control, e.g. only
> consider convexities above a certain scale as "bumps".
>
That would produce quite a lot of points, because usual heightfields contain
quite a lot of local maxima.
HF-Lab contains a function for something quite similar, namely filling up local
minima, source code (in C) can be found at:
http://www.best.com/~beale/
Christoph
--
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/
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On Sat, 1 Jul 2000 12:09:16 +0100, "Mick Hazelgrove"
<mic### [at] mhazelgrovefsnetcouk> wrote:
>Is there a way of finding the highest parts of a hf. I don't just want
>everything above a certain height but the top of every bump. Hope this is
>clear.
>
>Hope someone can help.
In MegaPOV, you can use the slope pattern and give it a suitable color
map so as to only point out the peaks. Then you can use eval_pigment
to check against it and the place objects or whatever you like on the
'bumps'. Hope I made this clear enough.
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG e-mail : pet### [at] tagpovrayorg
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Mick Hazelgrove wrote:
> Is there a way of finding the highest parts of a hf. I don't just want
> everything above a certain height but the top of every bump. Hope this is
> clear.
>
> Hope someone can help.
I believe this problem is a bit similar to a problem that is solved
by the source code I posted 13. May 2000 to the thread
"On Bezier splines" (by Peter Popov):
news://news.povray.org/391C9B3B.C63B6FC1%40online.no
I can explain how to use the code if you're interested.
Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html
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In article <shgslso0akn9pcm58dlljbqg9sbgg5c03u@4ax.com>, Peter Popov
<pet### [at] usanet> wrote:
> In MegaPOV, you can use the slope pattern and give it a suitable color
> map so as to only point out the peaks. Then you can use eval_pigment
> to check against it and the place objects or whatever you like on the
> 'bumps'. Hope I made this clear enough.
The eval_pigment function won't work with the slope pattern, because
slope requires intersection information which isn't available(POV
doesn't know you want to check it at that point on the surface of the
object).
However, you could do an overhead view of the height field, and use
eval_pigment on the resulting image_map...or emulate the slope pattern
using the trace function.
--
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/
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On Sat, 01 Jul 2000 19:43:28 -0500, Chris Huff <chr### [at] maccom>
wrote:
>The eval_pigment function won't work with the slope pattern, because
>slope requires intersection information which isn't available(POV
>doesn't know you want to check it at that point on the surface of the
>object).
That's a limitation I didn't think about. Thanks for putting me back
on track.
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG e-mail : pet### [at] tagpovrayorg
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Wouldn't a gradient y pattern be even better to determine the highest part
of the Hf? Just give it a colour-map from black to white and check for the
brightest part (with eval_pattern)?
Marc-Hendrik
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Margus Ramst wrote:
>A basic method in MegaPOV would be to get a grid of height values
>(using trace) and start comparing: if a point is higher than all 8
>points around it (or 5 points at the edges, or 3 points in the corner)
>it is the top of a bump.
If the base of your HF is an image you can use ImagInc by Remco de Korte
to get a grid of values: http://www.xs4all.nl/~remcodek/pov.html . It
turns an image into an INC file so you can use the RGB-data.
Ingo
--
Photography: http://members.home.nl/ingoogni/
Pov-Ray : http://members.home.nl/seed7/
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On Sun, 2 Jul 2000 11:36:53 +0200, "Marc-Hendrik Bremer"
<Mar### [at] t-onlinede> wrote:
>Wouldn't a gradient y pattern be even better to determine the highest part
>of the Hf? Just give it a colour-map from black to white and check for the
>brightest part (with eval_pattern)?
This would only determine the global maximum and not all the local
maxima.
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG e-mail : pet### [at] tagpovrayorg
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