So I've started working on an extremely simple 2d tiled sidescrolling engine, using pygame (i know, but pretty much only for rendering + input). The problem is that the way that I've set up collision detection causes an object to stop moving in all directions when it hits another object. Here's the code for collision detection:
[source lang="python"]


def checkcollision(ob1, ob2):
if(ob1.x+ob1.w > ob2.x and
ob1.x < ob2.x+ob2.w):
if(ob1.y+ob1.h > ob2.y and
ob1.y < ob2.y+ob2.h):
return True
else:
return False
else:
return False

def collision():
for atile in mainarea.tiles:
if(checkcollision(player,atile)):
player.move(-player.vx, -player.vy)
player.vx = 0
player.vy = 0
[/source]
My question is, how can I implement collision detection that will only stop movement along one axis, but allow the other axis to keep moving (cause 'sliding' along walls instead of sticking)?

I apoligize if I'm asking in the wrong place, but it seems like a rather general question, and I didn't want to put this under physics, as I do not think it qualifies.

Alright, i think i get what you're saying. So i don't need to check top, left, bottom, right, but rather x and y collision? Thanks for the help.

Paul Nettle's reference here explains a theory of how to do this. While the result is focused on 3D and ellipsoids, it does lead up to that by describing the method as it applies to 2D and circles. The section on sliding applies to things other than spheres either way and demonstrates how to get the sliding vector from the direction vector and obstacle plane.

just use box2d