502 lines
20 KiB
C#
502 lines
20 KiB
C#
/*
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* Farseer Physics Engine based on Box2D.XNA port:
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* Copyright (c) 2010 Ian Qvist
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*
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* Box2D.XNA port of Box2D:
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* Copyright (c) 2009 Brandon Furtwangler, Nathan Furtwangler
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*
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* Original source Box2D:
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* Copyright (c) 2006-2009 Erin Catto http://www.gphysics.com
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using FarseerPhysics.Collision;
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using FarseerPhysics.Collision.Shapes;
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using FarseerPhysics.Common;
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using Microsoft.Xna.Framework;
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namespace FarseerPhysics.Dynamics.Contacts
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{
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/// <summary>
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/// A contact edge is used to connect bodies and contacts together
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/// in a contact graph where each body is a node and each contact
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/// is an edge. A contact edge belongs to a doubly linked list
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/// maintained in each attached body. Each contact has two contact
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/// nodes, one for each attached body.
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/// </summary>
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public sealed class ContactEdge
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{
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/// <summary>
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/// The contact
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/// </summary>
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public Contact Contact;
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/// <summary>
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/// The next contact edge in the body's contact list
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/// </summary>
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public ContactEdge Next;
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/// <summary>
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/// Provides quick access to the other body attached.
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/// </summary>
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public Body Other;
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/// <summary>
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/// The previous contact edge in the body's contact list
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/// </summary>
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public ContactEdge Prev;
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}
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[Flags]
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public enum ContactFlags
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{
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None = 0,
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/// <summary>
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/// Used when crawling contact graph when forming islands.
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/// </summary>
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Island = 0x0001,
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/// <summary>
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/// Set when the shapes are touching.
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/// </summary>
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Touching = 0x0002,
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/// <summary>
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/// This contact can be disabled (by user)
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/// </summary>
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Enabled = 0x0004,
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/// <summary>
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/// This contact needs filtering because a fixture filter was changed.
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/// </summary>
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Filter = 0x0008,
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/// <summary>
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/// This bullet contact had a TOI event
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/// </summary>
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BulletHit = 0x0010,
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/// <summary>
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/// This contact has a valid TOI i the field TOI
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/// </summary>
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TOI = 0x0020
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}
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/// <summary>
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/// The class manages contact between two shapes. A contact exists for each overlapping
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/// AABB in the broad-phase (except if filtered). Therefore a contact object may exist
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/// that has no contact points.
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/// </summary>
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public class Contact
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{
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private static EdgeShape _edge = new EdgeShape();
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private static ContactType[,] _registers = new[,]
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{
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{
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ContactType.Circle,
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ContactType.EdgeAndCircle,
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ContactType.PolygonAndCircle,
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ContactType.LoopAndCircle,
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},
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{
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ContactType.EdgeAndCircle,
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ContactType.NotSupported,
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// 1,1 is invalid (no ContactType.Edge)
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ContactType.EdgeAndPolygon,
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ContactType.NotSupported,
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// 1,3 is invalid (no ContactType.EdgeAndLoop)
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},
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{
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ContactType.PolygonAndCircle,
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ContactType.EdgeAndPolygon,
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ContactType.Polygon,
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ContactType.LoopAndPolygon,
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},
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{
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ContactType.LoopAndCircle,
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ContactType.NotSupported,
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// 3,1 is invalid (no ContactType.EdgeAndLoop)
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ContactType.LoopAndPolygon,
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ContactType.NotSupported,
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// 3,3 is invalid (no ContactType.Loop)
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},
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};
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public Fixture FixtureA;
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public Fixture FixtureB;
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internal ContactFlags Flags;
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public Manifold Manifold;
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// Nodes for connecting bodies.
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internal ContactEdge NodeA = new ContactEdge();
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internal ContactEdge NodeB = new ContactEdge();
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public float TOI;
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internal int TOICount;
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private ContactType _type;
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private Contact(Fixture fA, int indexA, Fixture fB, int indexB)
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{
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Reset(fA, indexA, fB, indexB);
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}
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/// Enable/disable this contact. This can be used inside the pre-solve
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/// contact listener. The contact is only disabled for the current
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/// time step (or sub-step in continuous collisions).
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public bool Enabled
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{
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set
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{
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if (value)
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{
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Flags |= ContactFlags.Enabled;
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}
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else
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{
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Flags &= ~ContactFlags.Enabled;
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}
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}
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get { return (Flags & ContactFlags.Enabled) == ContactFlags.Enabled; }
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}
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/// <summary>
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/// Get the child primitive index for fixture A.
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/// </summary>
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/// <value>The child index A.</value>
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public int ChildIndexA { get; internal set; }
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/// <summary>
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/// Get the child primitive index for fixture B.
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/// </summary>
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/// <value>The child index B.</value>
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public int ChildIndexB { get; internal set; }
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/// <summary>
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/// Get the contact manifold. Do not modify the manifold unless you understand the
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/// internals of Box2D.
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/// </summary>
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/// <param name="manifold">The manifold.</param>
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public void GetManifold(out Manifold manifold)
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{
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manifold = Manifold;
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}
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/// <summary>
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/// Gets the world manifold.
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/// </summary>
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public void GetWorldManifold(out Vector2 normal, out FixedArray2<Vector2> points)
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{
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Body bodyA = FixtureA.Body;
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Body bodyB = FixtureB.Body;
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Shape shapeA = FixtureA.Shape;
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Shape shapeB = FixtureB.Shape;
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Collision.Collision.GetWorldManifold(ref Manifold, ref bodyA.Xf, shapeA.Radius, ref bodyB.Xf, shapeB.Radius,
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out normal, out points);
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}
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/// <summary>
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/// Determines whether this contact is touching.
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/// </summary>
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/// <returns>
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/// <c>true</c> if this instance is touching; otherwise, <c>false</c>.
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/// </returns>
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public bool IsTouching()
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{
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return (Flags & ContactFlags.Touching) == ContactFlags.Touching;
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}
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/// <summary>
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/// Flag this contact for filtering. Filtering will occur the next time step.
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/// </summary>
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public void FlagForFiltering()
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{
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Flags |= ContactFlags.Filter;
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}
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private void Reset(Fixture fA, int indexA, Fixture fB, int indexB)
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{
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Flags = ContactFlags.Enabled;
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FixtureA = fA;
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FixtureB = fB;
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ChildIndexA = indexA;
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ChildIndexB = indexB;
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Manifold.PointCount = 0;
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NodeA.Contact = null;
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NodeA.Prev = null;
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NodeA.Next = null;
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NodeA.Other = null;
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NodeB.Contact = null;
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NodeB.Prev = null;
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NodeB.Next = null;
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NodeB.Other = null;
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TOICount = 0;
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}
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/// <summary>
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/// Update the contact manifold and touching status.
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/// Note: do not assume the fixture AABBs are overlapping or are valid.
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/// </summary>
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/// <param name="contactManager">The contact manager.</param>
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internal void Update(ContactManager contactManager)
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{
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Manifold oldManifold = Manifold;
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// Re-enable this contact.
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Flags |= ContactFlags.Enabled;
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bool touching;
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bool wasTouching = (Flags & ContactFlags.Touching) == ContactFlags.Touching;
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bool sensor = FixtureA.IsSensor || FixtureB.IsSensor;
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Body bodyA = FixtureA.Body;
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Body bodyB = FixtureB.Body;
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// Is this contact a sensor?
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if (sensor)
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{
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Shape shapeA = FixtureA.Shape;
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Shape shapeB = FixtureB.Shape;
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touching = AABB.TestOverlap(shapeA, ChildIndexA, shapeB, ChildIndexB, ref bodyA.Xf, ref bodyB.Xf);
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// Sensors don't generate manifolds.
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Manifold.PointCount = 0;
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}
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else
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{
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Evaluate(ref Manifold, ref bodyA.Xf, ref bodyB.Xf);
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touching = Manifold.PointCount > 0;
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// Match old contact ids to new contact ids and copy the
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// stored impulses to warm start the solver.
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for (int i = 0; i < Manifold.PointCount; ++i)
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{
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ManifoldPoint mp2 = Manifold.Points[i];
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mp2.NormalImpulse = 0.0f;
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mp2.TangentImpulse = 0.0f;
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ContactID id2 = mp2.Id;
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bool found = false;
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for (int j = 0; j < oldManifold.PointCount; ++j)
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{
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ManifoldPoint mp1 = oldManifold.Points[j];
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if (mp1.Id.Key == id2.Key)
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{
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mp2.NormalImpulse = mp1.NormalImpulse;
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mp2.TangentImpulse = mp1.TangentImpulse;
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found = true;
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break;
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}
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}
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if (found == false)
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{
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mp2.NormalImpulse = 0.0f;
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mp2.TangentImpulse = 0.0f;
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}
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Manifold.Points[i] = mp2;
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}
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if (touching != wasTouching)
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{
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bodyA.Awake = true;
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bodyB.Awake = true;
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}
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}
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if (touching)
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{
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Flags |= ContactFlags.Touching;
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}
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else
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{
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Flags &= ~ContactFlags.Touching;
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}
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if (wasTouching == false && touching)
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{
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//Report the collision to both participants:
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if (FixtureA.OnCollision != null)
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Enabled = FixtureA.OnCollision(FixtureA, FixtureB, this);
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//Reverse the order of the reported fixtures. The first fixture is always the one that the
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//user subscribed to.
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if (FixtureB.OnCollision != null)
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Enabled = FixtureB.OnCollision(FixtureB, FixtureA, this);
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//BeginContact can also return false and disable the contact
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if (contactManager.BeginContact != null)
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Enabled = contactManager.BeginContact(this);
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//if the user disabled the contact (needed to exclude it in TOI solver), we also need to mark
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//it as not touching.
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if (Enabled == false)
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Flags &= ~ContactFlags.Touching;
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}
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if (wasTouching && touching == false)
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{
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//Report the separation to both participants:
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if (FixtureA != null && FixtureA.OnSeparation != null)
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FixtureA.OnSeparation(FixtureA, FixtureB);
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//Reverse the order of the reported fixtures. The first fixture is always the one that the
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//user subscribed to.
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if (FixtureB != null && FixtureB.OnSeparation != null)
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FixtureB.OnSeparation(FixtureB, FixtureA);
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if (contactManager.EndContact != null)
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contactManager.EndContact(this);
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}
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if (sensor)
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return;
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if (contactManager.PreSolve != null)
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contactManager.PreSolve(this, ref oldManifold);
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}
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/// <summary>
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/// Evaluate this contact with your own manifold and transforms.
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/// </summary>
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/// <param name="manifold">The manifold.</param>
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/// <param name="transformA">The first transform.</param>
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/// <param name="transformB">The second transform.</param>
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private void Evaluate(ref Manifold manifold, ref Transform transformA, ref Transform transformB)
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{
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switch (_type)
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{
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case ContactType.Polygon:
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Collision.Collision.CollidePolygons(ref manifold,
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(PolygonShape)FixtureA.Shape, ref transformA,
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(PolygonShape)FixtureB.Shape, ref transformB);
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break;
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case ContactType.PolygonAndCircle:
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Collision.Collision.CollidePolygonAndCircle(ref manifold,
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(PolygonShape)FixtureA.Shape, ref transformA,
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(CircleShape)FixtureB.Shape, ref transformB);
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break;
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case ContactType.EdgeAndCircle:
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Collision.Collision.CollideEdgeAndCircle(ref manifold,
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(EdgeShape)FixtureA.Shape, ref transformA,
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(CircleShape)FixtureB.Shape, ref transformB);
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break;
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case ContactType.EdgeAndPolygon:
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Collision.Collision.CollideEdgeAndPolygon(ref manifold,
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(EdgeShape)FixtureA.Shape, ref transformA,
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(PolygonShape)FixtureB.Shape, ref transformB);
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break;
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case ContactType.LoopAndCircle:
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LoopShape loop = (LoopShape)FixtureA.Shape;
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loop.GetChildEdge(ref _edge, ChildIndexA);
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Collision.Collision.CollideEdgeAndCircle(ref manifold, _edge, ref transformA,
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(CircleShape)FixtureB.Shape, ref transformB);
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break;
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case ContactType.LoopAndPolygon:
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LoopShape loop2 = (LoopShape)FixtureA.Shape;
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loop2.GetChildEdge(ref _edge, ChildIndexA);
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Collision.Collision.CollideEdgeAndPolygon(ref manifold, _edge, ref transformA,
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(PolygonShape)FixtureB.Shape, ref transformB);
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break;
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case ContactType.Circle:
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Collision.Collision.CollideCircles(ref manifold,
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(CircleShape)FixtureA.Shape, ref transformA,
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(CircleShape)FixtureB.Shape, ref transformB);
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break;
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}
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}
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internal static Contact Create(Fixture fixtureA, int indexA, Fixture fixtureB, int indexB)
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{
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ShapeType type1 = fixtureA.ShapeType;
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ShapeType type2 = fixtureB.ShapeType;
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Debug.Assert(ShapeType.Unknown < type1 && type1 < ShapeType.TypeCount);
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Debug.Assert(ShapeType.Unknown < type2 && type2 < ShapeType.TypeCount);
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Contact c;
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Queue<Contact> pool = fixtureA.Body.World.ContactPool;
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if (pool.Count > 0)
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{
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c = pool.Dequeue();
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if ((type1 >= type2 || (type1 == ShapeType.Edge && type2 == ShapeType.Polygon))
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&&
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!(type2 == ShapeType.Edge && type1 == ShapeType.Polygon))
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{
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c.Reset(fixtureA, indexA, fixtureB, indexB);
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}
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else
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{
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c.Reset(fixtureB, indexB, fixtureA, indexA);
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}
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}
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else
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{
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// Edge+Polygon is non-symetrical due to the way Erin handles collision type registration.
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if ((type1 >= type2 || (type1 == ShapeType.Edge && type2 == ShapeType.Polygon))
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&&
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!(type2 == ShapeType.Edge && type1 == ShapeType.Polygon))
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{
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c = new Contact(fixtureA, indexA, fixtureB, indexB);
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}
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else
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{
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c = new Contact(fixtureB, indexB, fixtureA, indexA);
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}
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}
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c._type = _registers[(int)type1, (int)type2];
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return c;
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}
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internal void Destroy()
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{
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FixtureA.Body.World.ContactPool.Enqueue(this);
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Reset(null, 0, null, 0);
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}
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#region Nested type: ContactType
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private enum ContactType
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{
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NotSupported,
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Polygon,
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PolygonAndCircle,
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Circle,
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EdgeAndPolygon,
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EdgeAndCircle,
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LoopAndPolygon,
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LoopAndCircle,
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}
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#endregion
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}
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} |