From: thinman@netcom.com (Lance Norskog)
Subject: TECH: Object collision & coprocessors
Date: Mon, 9 Mar 92 20:29:38 PST



The collision detection problem is one of the few "cleavage planes"
where VR software can be broken apart into co-processors.  

Given a separate copy of the world model, the simulator processor
can run the simulation a small number of time ticks ahead,
processing the known changes (objects flying around in straight lines)
and saving the state for the unfinished computation of each time tick.
The deferred computation for time T would then be finished at time T
given the latest mouse or glove input.  There is no great communication
bandwidth needed between the simulator and the main processor;
this last is the achilles heel of coprocessor-based systems.

The simulator can even apply predictive (Kalman) filtering to the
mouse and glove motions and tentatively do the collision prediction
anyway.  If the prediction for time T is with N% of the actual input
for time T, you just go ahead and use the predicted version instead.

Another major cleavage plane is sound generation.  Note that this
can also be generated and partially mixed down in advance using
the same techniques as the simulation processor.

Lance Norskog