On Wed, 17 Mar 2004 02:00:27 -0500, "Slime" <fak### [at] emailaddress>
wrote:

>
>That caught my eye too. I don't look at statistics often, so those may be
>typical percentages, but I dunno, they seem awfully low. Maybe you're doing
>something that makes bounding boxes inefficient?
>
> ...
>
>So, anyway, the thing that worries me the most is the ray intersection
>percentages. Are you using lots of intersections/differences, maybe? That,
>among other things, can cause bounding boxes to be so large that they don't
>help at all.

Yep - as you and others pointed out,  I rather screwed this up.  So,
then, perhaps (well, er, obviously) I don't understand how bounding
boxes work:

Let's say I have two long cylinders perpendicular to one another - a
'+' shape of some sort.

Separately, the bounding boxes would be tight around each cylinder.
If I place them in a union together, I've got one large bounding box,
which I suppose could be less efficient than two tight bounding boxes
done separately.  Er, am I right so far?

Now, how do I manually make my bounding boxes any better than a single
box surrounding my odd-shaped CSG?  I always (incorrectly?) pictured a
large CSG bounding box to be the 'initial' test.  If a ray hits it,
then all the individual bounding boxes inside the CSG would be
checked.

Can I 'turn off' my CSG bounding box, and just let the multiple (yet
tight) boxes suffice?


- How

Post a reply to this message