Hi Tracers!

As far as your suggestions for the reworking of my giant planet
Tmirdlalg (earlier this month) are concerned, meanwhile I downloaded
MegaPOV 0.6 and hope to start reading into it in the coming months.

Currently, I have another problem: since I discovered John Beale's
HF-Lab about two years ago (and a bit later also halfway practicable
ways to wrap the generated heightfields around spheres - of course, I
already hear you shouting "Isosurfaces! Isosurfaces! Isosurfaces!"... -
like Polyray's sheight_field, DMesh or now the greatly improved new
version of Beale's ORB), I played around with seamlessly tiling
heightfields for asteroid surfaces.

But to get naturally looking surface features not strangely distorted
towards the asteroid's poles, I have to convert the original heightfield
into a Simple Cylindrical Projection. I calculated a coarse
approximation with 10-degree latitude stripes and found out that the
original heightfield must have an x-y ratio of about 2:1.57 to yield a
map of 2:1 correctly gradually "squeezed" towards the poles.

Doing this manually is quite time-consuming (already with 10-degree
stripes) and also error-prone, and if one does not use very narrow
stripes, features in higher latitudes extending over stripe borders (e.
g. large craters) look irregular.

Does anyone of you know of a tool which automatically does this work -
with more sophisticated math, perhaps some integral algorithms?

My second question deals with craters: those of you who use HF-Lab might
know that its "crater" function simply adds the craters' relief onto the
existing surface, whereas in reality, crater impacts wipe out older
features below.

Does a heightfield processing tool for realistic cratering exist which
perhaps also emulates other features commonly associated with impact
craters like central mounds, ejecta blankets and scattered debris around
the crater, perhaps even partially collapsed crater walls?

Honestly said, for the more distant future (with computers at two-digit
GHz clock rates and some terabytes of RAM :-)) I dream of creating
asteroids as detailedly as the recent close-ups of Eros...

See you in Khyberspace!

Yadgar

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Yadgar wrote in message <3A6### [at] ndhnet>...
>Does anyone of you know of a tool which automatically does this work -
>with more sophisticated math, perhaps some integral algorithms?


There's a utility to do this to TGA image files that comes with the POV
Planetarium stuff.

--
Mark

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"Yadgar" <j.b### [at] ndhnet> wrote in message news:3A6### [at] ndhnet...
> Does a heightfield processing tool for realistic cratering exist which
> perhaps also emulates other features commonly associated with impact
> craters like central mounds, ejecta blankets and scattered debris around
> the crater, perhaps even partially collapsed crater walls?

Here's a link to a program that makes height fields with craters that look
very good (in my opinion, anyway):
http://daylongraphics.com/products/leveller/index.htm

Regards,
Dave

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Yadgar wrote:

> Does anyone of you know of a tool which automatically does this work -
> with more sophisticated math, perhaps some integral algorithms?

You might look for a tool called Wilber. Strange name, but it makes nice
planets.
Runs in Windows.

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For a synthetical planet an isosurface with pigment function is probably a
quite good idea, because you don't have problems with mapping and tiling.  

You might also have a look at:

http://www.schunter.etc.tu-bs.de/~chris/terlinks.html

and

http://www.povray.org/links/3D_Programs/Height_Field_Modelling_Programs_and_Utilities/


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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