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using System;
using System.Collections.Generic;
using FarseerPhysics.Dynamics;
using Microsoft.Xna.Framework;
namespace FarseerPhysics.Controllers
{
public enum GravityType
{
Linear,
DistanceSquared
}
public class GravityController : Controller
{
public List<Body> Bodies = new List<Body>();
public List<Vector2> Points = new List<Vector2>();
public GravityController(float strength)
: base(ControllerType.GravityController)
{
Strength = strength;
MaxRadius = float.MaxValue;
}
public GravityController(float strength, float maxRadius, float minRadius)
: base(ControllerType.GravityController)
{
MinRadius = minRadius;
MaxRadius = maxRadius;
Strength = strength;
}
public float MinRadius { get; set; }
public float MaxRadius { get; set; }
public float Strength { get; set; }
public GravityType GravityType { get; set; }
public override void Update(float dt)
{
Vector2 f = Vector2.Zero;
foreach (Body body1 in World.BodyList)
{
if (!IsActiveOn(body1))
continue;
foreach (Body body2 in Bodies)
{
if (body1 == body2 || (body1.IsStatic && body2.IsStatic) || !body2.Enabled)
continue;
Vector2 d = body2.WorldCenter - body1.WorldCenter;
float r2 = d.LengthSquared();
if (r2 < Settings.Epsilon)
continue;
float r = d.Length();
if (r >= MaxRadius || r <= MinRadius)
continue;
switch (GravityType)
{
case GravityType.DistanceSquared:
f = Strength / r2 / (float)Math.Sqrt(r2) * body1.Mass * body2.Mass * d;
break;
case GravityType.Linear:
f = Strength / r2 * body1.Mass * body2.Mass * d;
break;
}
body1.ApplyForce(ref f);
Vector2.Negate(ref f, out f);
body2.ApplyForce(ref f);
}
foreach (Vector2 point in Points)
{
Vector2 d = point - body1.Position;
float r2 = d.LengthSquared();
if (r2 < Settings.Epsilon)
continue;
float r = d.Length();
if (r >= MaxRadius || r <= MinRadius)
continue;
switch (GravityType)
{
case GravityType.DistanceSquared:
f = Strength / r2 / (float)Math.Sqrt(r2) * body1.Mass * d;
break;
case GravityType.Linear:
f = Strength / r2 * body1.Mass * d;
break;
}
body1.ApplyForce(ref f);
}
}
}
public void AddBody(Body body)
{
Bodies.Add(body);
}
public void AddPoint(Vector2 point)
{
Points.Add(point);
}
}
}
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