On Thu, 14 Feb 2002 21:36:41 GMT, Erk### [at] povrayorg (Erkki


>Difference is a tricky construction to autobound tightly, there's that
>nasty INVERSE keyword involved. In general a difference can't be
>bounded internally at lower levels than the whole object, if a ray
>hits the 'outer' object all 'inner' objects will have to be evaluated.
>As the number of 'inner' objects increase the total evaluation cost
>increases as well. 

I've often thought about a possible remedy of the situation and the
only thing I've come up with is the following:

Imagine the scene space split into 27 subspaces by the 6 planes that
define an object's bounding slab. The central subspace is finite and
the others are infinite but have some defined boundaries. When
calculating the bounding slabs for a difference, there will be 26
slabs (at most) in the hierarchy and not 1, but it could be faster
than no bounding at all (for the internal objects).


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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