Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!uunet!mcsun!ukc!canon!ads
From: ads@canon.co.uk (Adam Billyard)
Newsgroups: comp.graphics
Subject: Re: Spatial data structures again
Keywords: Ray tracing Spatial subdivision Voxel
Message-ID: <1991May24.140240.27603@canon.co.uk>
Date: 24 May 91 14:02:40 GMT
References: <1991May14.070444.18261@images.cs.und.ac.za> <1991May24.040551.2811@netcom.COM>
Reply-To: ads@canon.co.uk
Organization: Canon Research Europe, Guildford, UK
Lines: 19

thinman@netcom.COM (Lance Norskog) writes:

> BSP doesn't work well here by itself, because you have to re-BSP the
> scene per change.  Re-sorting the list per update doesn't work either,
> because it takes too long.  But, consider the following scene: a room

I think I'd take issues with this idea that you have to recompute the
BSP trees each time an object moves.  When the model is closed and
convex, then any transform short of inversion with be fine since there
is no crossing of planar boundaries from one half space to the other.

I've been thinking that when BSP trees are built, they should include
some sort of specification as to the space constraints imposed by the
root on the immediate children; if the transform leaves the subtree
still within this bounding volume (probably needs to be finer than a
bbox) then BSP recomputation is unnecessary. 


	Adam Billyard