I have been using the following code to check for collision detection for the player and the wall:



void Player::move()
{
player_outline.x += xVel;
if (...check_collision(player_outline, wall_outline))
player_outline.x -= xVel;

player_outline.y += yVel;
if (...check_collision(player_outline, wall_outline))
player_outline.y -= yVel;
}


This works fine but if there are a lot of different walls, barrels, obstacles, then the if statement will become quite large and system hogging. Is there a more efficient way to determine what to check/how to check for collision? I'm sure there must be.
Thanks in advance.

I'm more interested in writing it myself. Could you provide a link to an example?

I'm not worrying (or required to worry) about velocity, speed, or any other variables other than location. If you hit a wall, you should stop. I'm working with 2D strictly, yes.

Thanks

Glancing at the source it seems overly complicated for what I need it for but should be helpful nonetheless.

What you want is a "spatial query", which allows you to ask what objects are in a particular area. There are a bunch of ways to do that depending on the size of your world and range of sizes of your objects. I'll throw out some terms for you to google: Spatial Hash (what Chipmunk uses), Sweep and Prune or Mark and Sweep (what Box2D used to use), and Bounding Volume Hierarchy (what Box2D uses now).

I'd look at how Chipmunk does it since its system is a lot simpler.

Spatial Hash divides the world into a grid and places objects into whatever grid cells they overlap. This works particularly well if your game is tile-based, since most objects will end up in at most one grid cell. When adding or removing an object, find what cells it covers and add it to or remove it from the hash table using the grid coordinates of those cells as keys. To find what objects are in an area, go through each cell that the area covers and return any objects you find. Depending on size and position, objects can cover more than one grid cell at a time so you need to mark objects so you don't return them more than once. Increment a counter every time you run a query, store that value into the object record when you visit it, and only return an object if the counter and the stored value don't match.

If I understand correctly there should be a piece of data in an obstacle and the player that identifies it's location on a grid (possibly an array) so that the collision detection function can see what obstacles are near the player and might be causing a collision?

Like what KDMiller3 said, you should create a function that will tell you if there is nothing taking space in the location you want to move to. So like if(areaAvailabe(<where player wants to move>)) returns true then proceed to move the player there. Though it's mostly the reverse of what you're doing now.