gdalgorithms-list

[Algorithms] Simple player collision response problem

[Jason Z. <zi...@n-...>]

Hi everyone, I've been wrestling with a problem for the past few days and it
just won't go away.  :)  I've been rewriting my player vs. world collision
detection and response routines, and I've pretty much got it all finished
except for one problem.  When the player bumps into or walks along a crease
(where two polygon edges meet) the collision response algo seems to make him
oscillate.

So you'll be walking along in a shallow valley bouncing left and right a
tiny bit as you move down the crease.

I've taken a look at the quake source and it does something similiar to what
I'm doing, except it looks like there is some special case code just for
creases.  I'd really like to avoid hacking so I'm hoping some of
the experts on this list have run into this problem and solved it.  Or
can outline a simple "slide along polygons" collision response that handles
crease situations.

What I'm doing now is simply calculating a sliding plane based on the poly
the player is hitting and sliding him along that with the remaining velocity
after the initial collision.  I do this recursively each frame against the
environment until the velocity is so small I can just set it to zero.

Thanks for any help.

- Jason Zisk
- nFusion Interactive LLC

RE: [Algorithms] Simple player collision response problem

[Jaimi M. <ja...@al...>]

Hi Jason --

In my code (not the elliptical code that I still can't get to work right),
I handle this by adding invisible clipping solids. These are just polygons
that get added to the movement code, but not to the rendering code. This
lets me fine tune areas where problems like this arise. Unfortunately, this
doesn't work well for terrain, so I've kept my old terrain movement code,
which just interpolates heights from the heightmap.
I'm interested in what others are doing though, as I'll probably abandon
the height-interpolation method when I can get a real clipper in.

Jaimi


-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of Jason
Zisk
Sent: Thursday, September 07, 2000 11:42 AM
To: Algorithms List
Subject: [Algorithms] Simple player collision response problem


Hi everyone, I've been wrestling with a problem for the past few days and it
just won't go away.  :)  I've been rewriting my player vs. world collision
detection and response routines, and I've pretty much got it all finished
except for one problem.  When the player bumps into or walks along a crease
(where two polygon edges meet) the collision response algo seems to make him
oscillate.

So you'll be walking along in a shallow valley bouncing left and right a
tiny bit as you move down the crease.

I've taken a look at the quake source and it does something similiar to what
I'm doing, except it looks like there is some special case code just for
creases.  I'd really like to avoid hacking so I'm hoping some of
the experts on this list have run into this problem and solved it.  Or
can outline a simple "slide along polygons" collision response that handles
crease situations.

What I'm doing now is simply calculating a sliding plane based on the poly
the player is hitting and sliding him along that with the remaining velocity
after the initial collision.  I do this recursively each frame against the
environment until the velocity is so small I can just set it to zero.

Thanks for any help.

- Jason Zisk
- nFusion Interactive LLC







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