XNA 2D碰撞检测

Question

I was wondering where I could find some nice resource material on how I could write some clean collision detection coding.

I'm pretty new to XNA programming, and have a general understanding on how I would want to write my game, but I am having serious trouble with the idea of collision detection. It boggles my mind.

I know you can use the 2d boundingbox class. But after that, I'm stuck. I don't want to have to check if an object is colliding with EVERY single object in the game, so I was wondering if someone could point me in the right direction for either some literature on the matter or something.

Answer 1

If you are just trying to minimize the CPU detection work, check out QuadTree implementations. They basically break up your "scene" into smaller sections to optimize detection (example in C#): http://www.codeproject.com/Articles/30535/A-Simple-QuadTree-Implementation-in-C

If you are talking more about actual physics, check out the tutorials from the devs of N-Game: http://www.metanetsoftware.com/technique.html

Or just use an existing XNA physics engine, such as Farseer or Bullet.

Answer 2

It depends a great deal on the scale and implementation of your game. How are the objects organized? Is the game organized into maps, or is there only one screen? Which objects will be colliding with which other objects?

If the game is a small enough scale, you might not need to worry about it at all.

If not, consider:

• splitting the game into distinct maps, where the objects on one map will only collide with other objects on the same map

• organizing lists of enemies by type, so that you can check only the right kinds of object against each other. (ie: projectiles aren't checking against projectiles, etc...). For example, I use the following dictionaries so that I can check against only objects of a certain type, or only creatures that belong to a certain faction:

   private readonly Dictionary<Type, List<MapObject>> mTypeObjects = new Dictionary<Type, List<MapObject>>(); private readonly Dictionary<FACTION, List<MapObject>> mFactionCreatures = new Dictionary<FACTION, List<MapObject>>(); 

• for maximum efficiency, but a more challenging implementation, you can use space partitioning, where objects are organized by 'sector', allowing you to rule out far away objects instantly.