"Jim Charter" <jrc### [at] msncom> wrote in message 
news:414d9723@news.povray.org...
> Jeremy M. Praay wrote:
>> I've had this strange question going around in my head for awhile now, so 
>> I thought I would finally ask:
>>
>> My understanding of meshes is not complete, but in theory, it seems like 
>> it would possible to take a mesh object, and convert each of the mesh 
>> triangles (including normals) into dissected CSG spheres which are then 
>> scaled, rotated, and translated into place.
>>
>> Has anyone ever experimented with this?  Obviously, render time would be 
>> much slower, especially if many difference operations are involved, and 
>> it just might be impossible with today's hardware and todays' large 
>> meshes. Additionally, I would guess that uv_mapping would be out of the 
>> question without a specific patch that supports this.  Nevertheless, it 
>> could be a useful tool in some, if not many, situations.
>>
> Not sure where you are heading with it.  It would seem that you could take 
> any three points and generate a triangular shape from planes and use it to 
> difference a sphere surface but the edges would still be curved and not 
> follow a straight line between the points. ( iso_csg has a function for 
> generating a triangle from three points btw which could be used to clip 
> the sphere surface )  Also I have been playing with using complex 
> clippings of sphere surfaces to use as hair.  Actually it is kind of on 
> the back burning right now but it seemed quite fast rendering.  Don't know 
> if any of that relates to your problem.

Mike actually answered my question, but thanks to you and Warp for the extra 
information.

The IC_Triangle function (in ISOCSG.inc) is very close to what I would like. 
What I'm thinking of, is a fairly simple way of replacing a mesh (smooth 
triangles) with "real" surfaces.  If the IC_Triangle had the ability to pass 
the vertex normals as well, and actually have the normals changed into a 
real function-based surface, it would be, well, really cool.  In theory, 
such a feature could allow someone to completely replace a smooth triangle 
mesh with isosurfaces.

It sounds compelling to me, but I'm not sure I could pull-off something of 
this magnitude.  In my ideal world, it could be a patch which uses a new 
format (mesh3?), or alternately, it could read through a mesh2 object and 
convert it into something else (isosurfaces, perhaps).

To back up a little bit, I'm often annoyed by the artifacts that come as a 
result of the "smooth triangle" problem.  The problem becomes very visible 
at times (e.g. http://www.oyonale.com/ldc/images/fermeture_detail2.jpg 
[sorry Gilles]).  However, I see that the new PoseRay does surface 
subdivision now, which may aid in alleviating this problem.  So anyway, 
that's where I was going with this.

-- 
Jeremy
www.beantoad.com

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