[plug] realistic collision detection

[stephen.]

Ive been looking out for some source code in c or c++ for polygon
collision detection 
tried lotts of places and havent had any luck.
Ide rather plagurise previous code than create my own from scratch 
(its a complex problem which would take me some considerable time to
solve) ->

Anyone know of software or libaries for the problem outlined below. ?

ive got 2 convex polygons with both rotation and velocity, and
direction.
( ime trying to simulate 2 solid objects colliding )
I need to determin the following  
the impact point 
angle and velocity of the collision point
and time of impact and location of polygons at point of impact.

I need this info in order to accuratly model the result of the impact
(which will obviously change the velocity direction and rotation of the
objects based on their mass-inertia, rotational inertia and
center of rotation.) 


The time frame of the impact collision is relativly short since it's for
a real time 
simulation and collison's will be constantly checked for so it may be
possible to 
simplify or approximate and remove some of the requirements.

2D collisions ( polygons) is ok if 3D (cubes - 3D solids) is available
that's even better.