轉自:http://www.codeplex.com/FarseerPhysics/Thread/View.aspx?ThreadId=16522
I did a quick look through your most recent code and was kind of shocked to find out you still didn’t have a more efficient Broad Phase. So I decided to write one for your engine during my break. I tried to make it simple instead of optimized for ease of understanding.
public class SweepAndPrune
{
delegate void CollisionCallback(Wrapper w1, Wrapper w2);
class Wrapper
{
public Node xBegin;
public Node xEnd;
public Node yBegin;
public Node yEnd;
public Geometry geometry;
public List<Geometry> colliders;
public Wrapper(Geometry geometry)
{
this.geometry = geometry;
this.colliders = new List<Geometry>();
this.xBegin = new Node(this, true);
this.xEnd = new Node(this, false);
this.yBegin = new Node(this, true);
this.yEnd = new Node(this, false);
}
public void Update()
{
colliders.Clear();
xBegin.value = geometry.AABB.Min.X;
xEnd.value = geometry.AABB.Max.X;
yBegin.value = geometry.AABB.Min.Y;
yEnd.value = geometry.AABB.Max.Y;
}
}
class Node
{
public bool begin;
public float value;
public Wrapper wrapper;
public Node(Wrapper wrapper, bool begin)
{
this.wrapper = wrapper;
this.begin = begin;
}
}
List<Wrapper> wrappers = new List<Wrapper>();
List<Node> xList = new List<Node>();
List<Node> yList = new List<Node>();
public void AddGeometry(Geometry item)
{
Wrapper wrapper = new Wrapper(item);
wrappers.Add(wrapper);
xList.Add(wrapper.xBegin);
xList.Add(wrapper.xEnd);
yList.Add(wrapper.yBegin);
yList.Add(wrapper.yEnd);
}
public void RemoveDisposed()
{
if (wrappers.RemoveAll(delegate(Wrapper w) { return w.geometry.Body.IsDisposed; }) > 0)
{
xList.RemoveAll(delegate(Node n) { return n.wrapper.geometry.Body.IsDisposed; });
yList.RemoveAll(delegate(Node n) { return n.wrapper.geometry.Body.IsDisposed; });
}
}
public void Run()
{
Update();
RunAxis(xList, HandleFirstCollision);
RunAxis(yList, HandleSecondCollision);
}
/**//// <summary>
/// Updates the nodes and sorts them.
/// </summary>
void Update()
{
foreach (Wrapper wrapper in wrappers)
{
wrapper.Update();
}
xList.Sort(delegate(Node l, Node r) { return l.value.CompareTo(r.value); });
yList.Sort(delegate(Node l, Node r) { return l.value.CompareTo(r.value); });
}
/**//// <summary>
/// Runs the collision detection on a axis
/// </summary>
void RunAxis(List<Node> list, CollisionCallback callback)
{
LinkedList<Wrapper> proximityList = new LinkedList<Wrapper>();
foreach (Node node in list)
{
if (node.begin)
{
foreach (Wrapper wrapper in proximityList)
{
callback(node.wrapper, wrapper);
}
proximityList.AddLast(node.wrapper);
}
else
{
proximityList.Remove(node.wrapper);
}
}
}
/**//// <summary>
/// when there is a collsion along the first axis
/// and if there is no early fail conditions then they are
/// added to each others colliders list
/// </summary>
void HandleFirstCollision(Wrapper w1, Wrapper w2)
{
//if(early fail conditions) {return;}
w1.colliders.Add(w2.geometry);
w2.colliders.Add(w1.geometry);
}
/**//// <summary>
/// when there is a collision along the second axis then
/// it checks to see if there was a collision along the first.
/// if there is then the 2 geometries bounding boxes are colliding.
/// </summary>
void HandleSecondCollision(Wrapper w1, Wrapper w2)
{
if (w1.colliders.Contains(w2.geometry))
{
//this is a confirmed broadphase collision
//so add a new arbiter or something for
//w1.geometry and w2.geometry
}
}
}