"Christopher James Huff" <chr### [at] maccom> wrote:
> The only way to tell if part of the scene will be visible is to parse
> it. If you haven't parsed an object you have no information about it to
> judge visibility from. Some kind of progressive parsing where you parse
> some information, determine visibility, and conditionally continue
> parsing would be possible, but speedup would be minimal, and the
> description language would be barely human readable. The result would
> probably be much slower because of the work for determining if the
> object affects the final image.

You could do a bounding-sphere at the beginning of each element.  The parser
could then scan past the element quickly by checking open and close braces.
It would store the center and radius of the element.  Determining if the
element needs to be checked for ray collision is then simply a matter of
comparing the distance from the center of the bounding-sphere to the ray
with the radius of the bounding-sphere.  If it needs to be checked, the
parser would go back and read the entire element.

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