In article <oprwckljrimulnlm@localhost>, melundbe@mtu.edu wrote:

> NOpe, I have objects both inside and outside the toroid, and the trace 
> simply ignores the intersections with the inside.  At least I'm pretty 
> confident that it is.  I'll check again.

Now I have no idea what you're describing. The trace() function has 
nothing to do with object-object intersections, and any objects not 
passed to trace() simply do not exist, as far as it is concerned.


> The lumpiness is a function that combines a bozo colormap and some others 
> with the f_torus, giving the torus a hilly landscape, or lumps.  This is 
> the reason I'm not simply constructing a torus through other means.

So you are tracing against an isosurface...should have paid more 
attention. Could be problems with max_gradient, or something with the 
locations you're tracing from confusing the isosurface solver.
As for vector math, you could pretty easily build it out of a mesh, like 
the height field macros in shapes.inc, and do something similar to 
project points onto its surface. The trace() function would still be the 
simplest way to find a point on the surface, though.


> I did some experiments and have reached the unambiguous conclusion that 
> the trace function will not hit the inside of the torus.  If anyone can 
> claim they're sure it works for them, I don't know what to say.  I'm using 
> MegaPOV 1.0, by the way.

Your conclusion is simply wrong. The trace() function, when used 
properly, will hit any part of the surface of an object. There is 
nothing special about these surfaces, except for the fact that the 
object is relatively inaccurate.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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