Hi!
  I'm making a blob modeller and there is only one problem with it:
  For the preview I need to calculate a mesh from the blob data, just like
blob sculptor does (but possibly much more accurately). Any ideas how can
I do this?
  I will post info about the modeller when it gets usable...

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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I would surround the blob in a box grid.
shoot rays from the the grid intersections.
Find all intersections of the blob on the ray 
	(record the normal too)

and make a mesh from the intersection points.

and when normal of adjacent points vary too much maybe
create extra points.

Don't know how efficient this would be. (I've been toying
with doing this in pov for iso_surface in making a mesh object
with a save for later to speed things up. Though I may just
do it to the object declaration which would probably be better)

Nieminen Mika wrote:
> 
>   Hi!
>   I'm making a blob modeller and there is only one problem with it:
>   For the preview I need to calculate a mesh from the blob data, just like
> blob sculptor does (but possibly much more accurately). Any ideas how can
> I do this?
>   I will post info about the modeller when it gets usable...
> 
> --
> main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
> *_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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Matthew Corey Brown - XenoArch <xen### [at] mindspringcom> wrote:
: I would surround the blob in a box grid.
: shoot rays from the the grid intersections.
: Find all intersections of the blob on the ray 
: 	(record the normal too)

: and make a mesh from the intersection points.

  I don't know how to calculate the intersection of a ray and a blob.

  And I forgot to mention that I want fully transformable (translate,
non-uniform scale, rotate) blob components (both spherical and cylindrical),
just as in povray. I want to make a _good_ blob modeller :)

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

Post a reply to this message

look at the pov source as long as you don't copy the code just the
algorithm, it should help you in the right direction. In general the
algorithm isn't copyrighted just the code itself. Though the blob speed
ups probably are. (Though those are so confusing to me) If your going to
do this for windows you may want to look at the gui extensions legal
ease to see if you can comply to that and then just use povrays own 
functions. Not sure if it would be allowed though.

Nieminen Mika wrote:
> 
> Matthew Corey Brown - XenoArch <xen### [at] mindspringcom> wrote:
> : I would surround the blob in a box grid.
> : shoot rays from the the grid intersections.
> : Find all intersections of the blob on the ray
> :       (record the normal too)
> 
> : and make a mesh from the intersection points.
> 
>   I don't know how to calculate the intersection of a ray and a blob.
> 
>   And I forgot to mention that I want fully transformable (translate,
> non-uniform scale, rotate) blob components (both spherical and cylindrical),
> just as in povray. I want to make a _good_ blob modeller :)
> 
> --
> main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
> *_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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On Sun, 03 Jan 1999 18:40:43 -0800, 
	Matthew Corey Brown - XenoArch <xen### [at] mindspringcom> wrote:
>look at the pov source as long as you don't copy the code just the
>algorithm, it should help you in the right direction. In general the
>algorithm isn't copyrighted just the code itself. Though the blob speed
>ups probably are. (Though those are so confusing to me) If your going to
>do this for windows you may want to look at the gui extensions legal
>ease to see if you can comply to that and then just use povrays own 
>functions. Not sure if it would be allowed though.

GUI extensions are forbidden to access POV-Ray through any but the 
documented interfaces.  Access to object intersection functions is 
not part of that interface.  

There is an equation for blobs; they could be treated as isosurfaces, 
following the general algorithm on R. Suzuki's web page.  Or, you can 
use something like Marching Cubes to find the interior surfaces as a 
triangle mesh; see the comp.graphics.algorithms FAQ parts 5.10 and 5.11 
for more info, references, and links, including patent restrictions:
(I've had to separate this URL onto two lines to keep it under 80
characters as my posting software requires; the clever reader will know 
how to fix it.)

http://www.cis.ohio-state.edu/hypertext/faq/usenet/
graphics/algorithms-faq/faq.html

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