Ron Parker wrote:

> Only the object it comes in contact with, in this case, but only because
> you picked such an easy plane.
> 
> POV computes the bounding box of the intersection by intersecting the
> bounding boxes of its constituents.  If a plane is axis-aligned, as
> yours is, its bounding box is the half-space that would be considered
> its "inside".  So the intersection of the two bounding boxes is the
> half of the union's bounding box that is inside the plane.
> 
> Had you intersected with plane {x+y,0}, however, this optimization would
> not have happened.  You could still attempt to bound it manually.

I suspected this was the case since some CSG operations on groups
of objects seem to operate much faster than they do on others.

Thanks for the input,

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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