High!

During Christmas, I tried to generate a spherical mesh from a 2000 x
1000 bumpmap of the
Moon... and after returning from my relatives, I had to realize that
parsing bogged down the
computer completely! After 2 days and 15 minutes, only 270 lines of the
bumpmap had been
parsed (I added a #warning statement giving the current line number)!
Obviously, the time needed
to parse spherical meshes (or meshes in general) increases
exponentially, so that on my computer,
a halfway realistic mesh e. g. of Earth would take decades or even
centuries to parse!

The only way to speed things up I could imagine would be limiting the
parsing process only to triangles actually visible in the
scene (so with a planetary object, the maximum would be 50 % of the
surface) - but even this would take a pretty long time.

So I ask you whether it could be possible to interrupt and resume the
parsing - as I live in a one-room flat with no chance to
stow away the computer at night, and the fans are loud enough to keep me
from sleeping.

And are there other ways to accelerate parsing?

See you in Khyberspace!

Yadgar

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news:3FEED1ED.3D93198B@gmx.de...
> And are there other ways to accelerate parsing?

Perhaps you could have a look at Christoph Hormann's page where he describes
how to obtain such effects in POV-Ray with isosurfaces rather than meshes :
http://www-public.tu-bs.de:8080/~y0013390/pov/planets.html

G.


-- 
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

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> So I ask you whether it could be possible to interrupt and resume the
> parsing - as I live in a one-room flat with no chance to
> stow away the computer at night, and the fans are loud enough to keep me
> from sleeping.
>
Maybe a suspend to disk will do ? Never tried , but this is the best bet I
could come with ...

> And are there other ways to accelerate parsing?
>
As Gilles said, look at the isosurface technique. If you have a grayscale
cylindrical
projection of the topography, then look at the IC_HF_Sphere macro of
Christoph's
IsoCSG package.
You may also determine the angular coordinates of the visible perimeter,
then generate only the visible mesh ...

Also , when rendering planetary surfaces, beware of floating point precision
problems ...
Usually topographic data from probes are expressed in meters,
(at least it is the case with Clementine) which may not be the unit you want
when rendering the entire globe (moon radius is around 1738000 meters,
a number povray considers infinite)

Good luck,

--
pascal.

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> High!
> 
> During Christmas, I tried to generate a spherical mesh from a 2000 x
> 1000 bumpmap of the
> Moon... and after returning from my relatives, I had to realize that
> parsing bogged down the
> computer completely! After 2 days and 15 minutes, only 270 lines of the

> bumpmap had been
> parsed (I added a #warning statement giving the current line number)!
> [...]

Your code must be quite inefficient in this case, generating a mesh of 2 

million vertices in SDL should be possible without too much trouble. 
Try the HF_Sphere macro in 'shapes.inc'.

> 
> So I ask you whether it could be possible to interrupt and resume the
> parsing - as I live in a one-room flat with no chance to
> stow away the computer at night, and the fans are loud enough to keep m
e
> from sleeping.

You get used to it after a while...

Interruptible parsing would be extrmely difficult to implement.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 25 Oct. 2003 _____./\/^>_*_<^\/\.______

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Even a mesh of the size you're describing shouldn't take *that* long to
generate. Why don't you post your code, maybe there's something in it that's
slowing it down.

> The only way to speed things up I could imagine would be limiting the
> parsing process only to triangles actually visible in the
> scene

You can't determine if an object is within the scene until you have parsed
it. If you wanted an optimization like this, you would need to implement it
manually with SDL code.

> So I ask you whether it could be possible to interrupt and resume the
> parsing - as I live in a one-room flat with no chance to
> stow away the computer at night, and the fans are loud enough to keep me
> from sleeping.

You can write a piece of SDL code which outputs the mesh to a file, line by
line. You could then set variables to the starting and ending lines, and
have it append output each time you run to the same file. In this way you
could generate your mesh in multiple passes, manually setting the
starting/ending lines as necessary each time.

 - Slime
 [ http://www.slimeland.com/ ]

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