Re: [PyOpenGL-Users] Collision Detections

[Richard J. <ric...@op...>]

On Friday 02 January 2004 11:30, Yannick Gingras wrote:
> just a quick question, how do you do your collision detections ?

Personally, I've not implemented such a beast yet. I believe a standard=20
approach is to have several levels of accuracy:

1. for all objects, determine a bounding sphere or box (your preference),
2. group those bounding objects in space using an octree to do broad=20
elimination of objects that are too far apart to bother each other,
3. for all objects that may be close enough, use the bounding object to see=
=20
whether they're close enough to collide,
4. if you're a) using boxes and b) the boxes are a good enough approximatio=
n=20
for you, then you're done, otherwise
5. perform per-plane/line/vertex collision detection.


> I made a few quick tests with pure python implementation based on
> map() and lists to store vertex coordinates. The performance is=20
> understandably really bad, I drop to 1/5 of the FPS I had before
> collision detection.

Note that any implementation using map() will incur a function call overhea=
d,=20
which is slow if you're not using a builtin function. Use a for loop instea=
d.=20
=46or some other optimisation techniques, see:

   http://www.py3d.org/py3d_zwiki/OptimisationHints

and the links from:

   http://simon.incutio.com/archive/2003/10/28/optimisingPython


> Is there a way to implement a decent collision detection in pure
> python or will I have to rely on C++ binding ?

I'd recommend that you first look at your algorithm - it's almost always=20
easier (and better) to optimise your code than to push it off to C or C++.=
=20
I've previously gone down the path of reimplementing core functionality in =
C=20
with some gain, but then a different approach proved to give a much better=
=20
gain, with no C code.

BTW, you don't *need* to use C++, unless you have a particular liking for i=
t.=20
C will do fine.


     Richard