In article <39c4d492@news.povray.org>, Geoff Wedig 
<wed### [at] darwinepbicwruedu> wrote:

> Now, there are ways to do this with isosurfaces (I think, but my 
> experience with isos is very minimal)  using a function which tests 
> against an object (after transforming coordinants) and returns -1 if 
> inside, 0 if outside, but I'm not certain isos can handle functions 
> like that

This would be the object pattern. The isosurface algorithm has trouble 
finding the intersections and normals for these types of patterns, the 
sharp discontinuity causes problems.


> (is there a function to find the shortest distance to the surface of 
> an arbitrary object?  That's what we really need in this case)

That is what my proximity pattern calculates. However, it is slow, and 
noise in the result makes isosurfaces intolerably slow.


> So, since I am not a POV guru, does this exist in some form, or is it 
> easier than I think with iso surfaces?  Do people think this would be 
> a useful feature?

It is quite easy to do with isosurfaces once you have a function for the 
object, just substitute functions which calculate the 
cylinderical/spherical coordinates for the xyz coordinates. To do this 
with other primitives could require an isosurface calculation mode for 
most of them, and would probably be impossible for some, and would be 
less flexible than just using an isosurface.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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