Greetings,

I've been making an object library which allows me to make beveled, 
filleted and chamfered objects, to be used for stone pillars and the 
like. Not wanting to deal with slow csg operations, I opted to make 
everything from basic shapes with the clipped_by modifier applied.

It all works very well, since the (hollow) surfaces meet up with each 
other if used properly. To see how well, I tested the closed objects 
with interior_texture, transparency, media, refraction, and interior 
attenuation. All these features work as they should, and the render time 
is relatively fast, as expected.

The problems come when I try to apply traditional csg techniques to my 
objects (difference, merge, intersection). Strange artifacts appear, 
such as transparent planes, partial csg results, and other strange things.

I'd rather not post my code here, as the definition for each object is 
rather large.

Has anyone else encountered strange results when trying to difference, 
intersect or merge unions of clipped_by objects? Was there a workaround? 
I'm beginning to think there isn't a solution....

Sam

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Samuel Benge <stb### [at] THIShotmailcom> wrote:
> Greetings,
>
> I've been making an object library which allows me to make beveled,
> filleted and chamfered objects, to be used for stone pillars and the
> like. Not wanting to deal with slow csg operations, I opted to make
> everything from basic shapes with the clipped_by modifier applied.
>
> It all works very well, since the (hollow) surfaces meet up with each
> other if used properly. To see how well, I tested the closed objects
> with interior_texture, transparency, media, refraction, and interior
> attenuation. All these features work as they should, and the render time
> is relatively fast, as expected.
>
> The problems come when I try to apply traditional csg techniques to my
> objects (difference, merge, intersection). Strange artifacts appear,
> such as transparent planes, partial csg results, and other strange things.
>
> I'd rather not post my code here, as the definition for each object is
> rather large.
>
> Has anyone else encountered strange results when trying to difference,
> intersect or merge unions of clipped_by objects? Was there a workaround?
> I'm beginning to think there isn't a solution....
>
> Sam

Good initiative!

Unfortunately, I nearly never happen to use objects with clipped_by, and I
can't be of much help for your problem. Hope someone else can.

Bruno.

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Samuel Benge nous apporta ses lumieres en ce 2007/10/11 18:05:
> Greetings,
> 
> I've been making an object library which allows me to make beveled, 
> filleted and chamfered objects, to be used for stone pillars and the 
> like. Not wanting to deal with slow csg operations, I opted to make 
> everything from basic shapes with the clipped_by modifier applied.
> 
> It all works very well, since the (hollow) surfaces meet up with each 
> other if used properly. To see how well, I tested the closed objects 
> with interior_texture, transparency, media, refraction, and interior 
> attenuation. All these features work as they should, and the render time 
> is relatively fast, as expected.
> 
> The problems come when I try to apply traditional csg techniques to my 
> objects (difference, merge, intersection). Strange artifacts appear, 
> such as transparent planes, partial csg results, and other strange things.
> 
> I'd rather not post my code here, as the definition for each object is 
> rather large.
> 
> Has anyone else encountered strange results when trying to difference, 
> intersect or merge unions of clipped_by objects? Was there a workaround? 
> I'm beginning to think there isn't a solution....
> 
> Sam
It could be a bounding problem.
Have you tried adding: bounded_by { clipped_by }? This will add a manual 
bounding conforming to the clipping object.

-- 
Alain
-------------------------------------------------
Unitarianism: Come let us reason together about this shit.

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Alain wrote:
> It could be a bounding problem.
> Have you tried adding: bounded_by { clipped_by }? This will add a manual 
> bounding conforming to the clipping object.

I tried several variations of your suggestion, and either nothing 
worked, or it made things worse. I will have to try a simpler test to 
see if I can find success.

Sam

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Samuel Benge <stb### [at] thishotmailcom> wrote:
> The problems come when I try to apply traditional csg techniques to my 
> objects (difference, merge, intersection). Strange artifacts appear, 
> such as transparent planes, partial csg results, and other strange things.

  A short example scene demonstrating the problem would be helpful.

  My guess is that it's the infamous coincident surfaces problem.
(I actually don't know if this problem happens if two *clipping* surfaces
coincide, but it could well be.)

-- 
                                                          - Warp

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Alain <ele### [at] netscapenet> wrote:
> Samuel Benge nous apporta ses lumieres en ce 2007/10/11 18:05:

> > Has anyone else encountered strange results when trying to difference,
> > intersect or merge unions of clipped_by objects? Was there a workaround?
> > I'm beginning to think there isn't a solution....
> >
> > Sam
>
> It could be a bounding problem.
> Have you tried adding: bounded_by { clipped_by }? This will add a manual
> bounding conforming to the clipping object.
>

I have a suggestion--which may not have any relevance--but you might try
changing Remove_Bounds=on/off and/or Bounding_Threshold=*some integer* in your
..INI file. That has helped me in some *odd* situations. Sorry I can't be more
specific as to *why* this trick (sometimes) works; I don't quite understand it
myself. The default Bounding_Threshold in POV-Ray is 3--or so it seems--not 25
as mentioned in the docs. Try alternately changing it to 1, or to 50 or more
(i.e., two extremes.)

I'd be curious to know if this helps.

Ken

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