Re: [Algorithms] Kinematic Collision

[David B. <db...@fa...>]

Hi,

About the inner/outer hull method, I think this is definitely the way to
go. Plus using recursion to handle sliding etc. (multiple checks to
handle gravity(sweep down), stepping(a sweep at a higher offset),
climbing, crouching etc).

I found that the most important thing to make this work is a very robust
sweep test(including hit normal etc). The sweep should also handle
initial intersection (no matter what you do 8h1t Happens(tm)) giving a
sensible depenetration vector and a distance to move to depenetrate the
objects. Pair wise seems good enough, although it would probably be
possible to make this recursive as well.

Since I added initial penetration handling my controller has not had any
problems, including moving lifts/platforms.

About using the PhysX stuff, I would say the CCD is OK for demo/basic
use but is probably not modular enough to do something more
sophisticated (eg Tomb Raider style) it doesnt have the concept of
states/transitions plus it seems too tied to the underlying geometric
database.

I also decided not to use the PhysX sweeps in my hobby project for a
couple of reasons, ie I didn't want to call into native code for every
shape query(this is XNA). Plus I think that handling of initial
intersection is "undefined". Not sure if this is still the case? (Any
idea Pierre?)

David 


On Wed, 02 Sep 2009 14:45 +0200, "Johan Gustafsson"
<spi...@gm...> wrote:
> Thanks for the feedback, very helpful.
> 
> About the the inner hull sweeptest, this is kinda inverted to my bias,
> with my bias I did a sweep 
> using a larger hull and then when finding collision i calculate the
> position to intersection and
> subtract the bias. To me they are both the same but I'll definitely give
> it a try.
> 
> Using rigid bodies seems to me much more problematic and having to
> control the character using impulse/forces
> is the main reason I choose the first method.
> 
> 
> James Robertsson Wrote:
> /"Get rid of your bias.  It sounds like a hack and, from what you say, 
> isn't helping.  My guess is you're seeing problems because of bugs in 
> your code that actually calculates the collision times.  (Ie the 
> capsule/primitive intersection functions.)"
> /
> I'm actually using PhysX SDK for collision detection and working under
> the assumption that it
> should be very stable and problem free, but who knows.
> 
> 
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