In article <6dS### [at] econymdemoncouk>, Mike Williams 
<mik### [at] econymdemoncouk> wrote:

> Wasn't it Simen Kvaal who wrote:
> >You seem to know these built-in-functions well!
> 
> It didn't start out that way. It took a lot of hard work to obtain all
> that information.

I'll bet! I personally avoid using the built-in functions(the syntax is 
awful, and I highly doubt it would survive if these functions are 
included in the official version), but this is very useful information 
for those who do use them.


> A subtle, and not quite intentional, side effect of the presence of my
> container surfaces is that they clobber the parts where the surface runs
> round the contained_by sphere. Because my transparent container surfaces
> are exactly coincident with the contained_by surface, only one of them
> gets rendered, and that happens to be the transparent surface.

I suggest something like "scale 1.001" to remedy this...or maybe "scale 
0.999", so those parts stand out as container-intersections. This could 
make debugging functions easier, since you could immediately see that 
the problem is a container intersecting with the surface.


> An alternative solution is to add the keyword "open" just after the
> contained_by statement.

Note that this solution doesn't help if your object contains media or is 
used in CSG...though "open inverse" should work. I would suggest just 
using a negative threshold, or declaring the function(a good practice 
anyway) and using it's negative("-FuncName(x,y,z)").
Or use "sign -1". :-)

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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