我使用各种形状进行碰撞检测(Rectangle
,Circle
,Cone
,Ring
等。)所有这些形状都是从基本抽象Shape
派生的类。我的游戏对象具有Shape类型的属性。
class GameObject
{
(...)
public Shape CollisionShape { get; set; }
}
在初始化过程中,我决定每个对象使用什么形状,例如:
GameObject person = new GameObject();
person.CollisionShape = new Circle(100); // 100 is radius
现在,当我想检查两个对象是否相交时,我使用以下类:
public class IntersectionChecker
{
public bool Intersect(Shape a, Shape b)
{
Type aType = a.GetType();
Type bType = b.GetType();
if( aType == typeof(Rectangle) && bType == typeof(Rectangle))
return Intersect(a as Rectangle, b as Rectangle);
if( aType == typeof(Rectangle) && bType == typeof(Circle))
return Intersect(a as Rectangle, b as Circle);
// etc. etc. All combinations
}
private bool Intersect(Rectangle a, Rectangle b)
{
// check intersection between rectangles
}
}
所以我的代码看起来像:
IntersectionChecker ic = new IntersectionCHecker();
bool isIntersection =
is.Intersect(personA.CollisionShape, personB.CollisionShape);
有没有更好的方法来实现我的目标,而没有在IntersectionChecker类中进行过几十次'if'检查和类型检查?
修改
请注意,检查形状A和B之间的交点的方法可用于检查B和A之间的交点。在许多答案中(感谢您的所有想法!)建议从形状本身而不是IntersectionChecker对象调用交叉检查。我认为它会迫使我重复代码。现在我可以这样做:
if( aType == typeof(Rectangle) && bType == typeof(Circle))
return Intersect(a as Rectangle, b as Rectangle);
if( aType == typeof(Circle) && bType == typeof(Rectangle))
return Intersect(b as Rectangle, a as Circle); // same method as above
答案 0 :(得分:12)
您可以使用Visitor Pattern,here is a C# example
这将允许您简单地使用Shape.Intersect(Rectangle),Shape.Intersect(Circle),...每个派生形状实现的方法。它会阻止您以额外的方法调用为代价对类型进行任何反射。
编辑 - 这是一个示例实现,如果没有可以在Shape中使用的共享功能,那么使用接口IShape可能会更清晰,但我只是停留在一个抽象基类中。
public class GameObject
{
private Shape _collisionShape;
public GameObject(Shape collisionShape)
{
_collisionShape = collisionShape;
}
public bool Intersects(GameObject other)
{
return _collisionShape.IntersectVisit(other._collisionShape);
}
}
public abstract class Shape
{
public abstract bool IntersectVisit(Shape other);
public abstract bool Intersect(Circle circle);
public abstract bool Intersect(Rectangle circle);
}
public class Circle : Shape
{
public override bool IntersectVisit(Shape other)
{
return other.Intersect(this);
}
public override bool Intersect(Circle circle)
{
Console.WriteLine("Circle intersecting Circle");
return false; //implement circle to circle collision detection
}
public override bool Intersect(Rectangle rect)
{
Console.WriteLine("Circle intersecting Rectangle");
return false; //implement circle to rectangle collision detection
}
}
public class Rectangle : Shape
{
public override bool IntersectVisit(Shape other)
{
return other.Intersect(this);
}
public override bool Intersect(Circle circle)
{
Console.WriteLine("Rectangle intersecting Circle");
return true; //implement rectangle to circle collision detection
}
public override bool Intersect(Rectangle rect)
{
Console.WriteLine("Rectangle intersecting Rectangle");
return true; //implement rectangle to rectangle collision detection
}
}
示例代码调用它:
GameObject objectCircle = new GameObject(new Circle());
GameObject objectRect = new GameObject(new Rectangle());
objectCircle.Intersects(objectCircle);
objectCircle.Intersects(objectRect);
objectRect.Intersects(objectCircle);
objectRect.Intersects(objectRect);
产生输出:
Circle intersecting Circle
Rectangle intersecting Circle
Circle intersecting Rectangle
Rectangle intersecting Rectangle
答案 1 :(得分:5)
您可以按照Shape类执行碰撞检查,向Shape添加IntersectsWith(Shape other)
方法。我还建议您在IntersectsWith(GameObject other)
添加GameObject
,以便将CollisionShape保密。
答案 2 :(得分:1)
如果支票无论如何都必须驻留在某处。
您可以向Intersects
添加Shape
方法:
abstract class Shape
{
public abstract Boolean Intersects(Shape other);
}
然后在Intersect
IntersectionChecker
中制作public static
方法,并针对每个具体形状实施Intersects
方法:
class Rectangle : Shape
{
public override Boolean Intersects(Shape other)
{
if (other is Rectangle)
{
return IntersectionChecker.Intersect(this, (Rectangle)other);
}
else if (other is Circle)
{
return IntersectionChecker.Intersect(this, (Circle)other);
}
throw new NotSupportedException();
}
}
答案 3 :(得分:1)
对于您的问题,没有简单的解决方案。您需要的是“双重调度”,它仅在Smalltalk或Lisp等语言中受支持。如果添加一个新类,所有提议的解决方案都将强制您更改所有派生类。这是糟糕的代码!
我会像这样解决问题:在没有任何交集代码的情况下实现Shape派生类。然后像这样实现一个Intersection类:
public class Intersection {
public bool Intersect(Shape a, Shape b) {....}
private bool Intersect(Rectangle a, Circle b) {...}
private bool Intersect(Circle a, Circle b) {...}
}
公共方法分析传入的形状并将工作调度( - >双重调度)到匹配的私有方法。其中包含原始交叉逻辑。 Intersect的实现不需要“ifs”。您可以使用反射来查找最佳匹配方法。详细信息取决于您的具体要求以及如何根据性能来衡量复杂性。但是,通过简单的直接实现开始很容易。因为所有内容都封装在一个地方,所以以后很容易优化。在我看来,这是一个很好的方法。 ; - )