com.almasb.fxgl.physics.box2d.dynamics.contacts.Contact Maven / Gradle / Ivy
/*
* FXGL - JavaFX Game Library. The MIT License (MIT).
* Copyright (c) AlmasB ([email protected]).
* See LICENSE for details.
*/
package com.almasb.fxgl.physics.box2d.dynamics.contacts;
import com.almasb.fxgl.core.math.FXGLMath;
import com.almasb.fxgl.physics.box2d.callbacks.ContactListener;
import com.almasb.fxgl.physics.box2d.collision.ContactID;
import com.almasb.fxgl.physics.box2d.collision.GenericCollision;
import com.almasb.fxgl.physics.box2d.collision.Manifold;
import com.almasb.fxgl.physics.box2d.collision.ManifoldPoint;
import com.almasb.fxgl.physics.box2d.collision.shapes.Shape;
import com.almasb.fxgl.physics.box2d.common.Transform;
import com.almasb.fxgl.physics.box2d.dynamics.Body;
import com.almasb.fxgl.physics.box2d.dynamics.Fixture;
import com.almasb.fxgl.physics.box2d.pooling.IWorldPool;
/**
* The class manages contact between two shapes.
* A contact exists for each overlapping AABB in the broad-phase (except if filtered).
* Therefore a contact object may exist that has no contact points.
*
* @author daniel
*/
public abstract class Contact {
// Flags stored in m_flags
// Used when crawling contact graph when forming islands.
public static final int ISLAND_FLAG = 0x0001;
// Set when the shapes are touching.
public static final int TOUCHING_FLAG = 0x0002;
// This contact can be disabled (by user)
public static final int ENABLED_FLAG = 0x0004;
// This contact needs filtering because a fixture filter was changed.
public static final int FILTER_FLAG = 0x0008;
public static final int TOI_FLAG = 0x0020;
public int m_flags;
// World pool and list pointers.
public Contact m_prev;
public Contact m_next;
// Nodes for connecting bodies.
public ContactEdge m_nodeA = new ContactEdge();
public ContactEdge m_nodeB = new ContactEdge();
public Fixture m_fixtureA = null;
public Fixture m_fixtureB = null;
public int m_indexA;
public int m_indexB;
public final Manifold m_manifold = new Manifold();
public float m_toiCount;
public float m_toi;
public float m_friction;
public float m_restitution;
public float m_tangentSpeed;
protected final IWorldPool pool;
protected Contact(IWorldPool argPool) {
pool = argPool;
}
/** initialization for pooling */
public void init(Fixture fA, int indexA, Fixture fB, int indexB) {
m_flags = ENABLED_FLAG;
m_fixtureA = fA;
m_fixtureB = fB;
m_indexA = indexA;
m_indexB = indexB;
m_manifold.pointCount = 0;
m_prev = null;
m_next = null;
m_nodeA.contact = null;
m_nodeA.prev = null;
m_nodeA.next = null;
m_nodeA.other = null;
m_nodeB.contact = null;
m_nodeB.prev = null;
m_nodeB.next = null;
m_nodeB.other = null;
m_toiCount = 0;
m_friction = mixFriction(fA.getFriction(), fB.getFriction());
m_restitution = mixRestitution(fA.getRestitution(), fB.getRestitution());
m_tangentSpeed = 0;
}
/**
* Get the contact manifold. Do not set the point count to zero. Instead call Disable.
*/
public Manifold getManifold() {
return m_manifold;
}
/**
* @return is this contact touching
*/
public boolean isTouching() {
return (m_flags & TOUCHING_FLAG) == TOUCHING_FLAG;
}
/**
* Enable/disable this contact. This can be used inside the pre-solve contact listener. The
* contact is only disabled for the current time step (or sub-step in continuous collisions).
*
* @param flag
*/
public void setEnabled(boolean flag) {
if (flag) {
m_flags |= ENABLED_FLAG;
} else {
m_flags &= ~ENABLED_FLAG;
}
}
public boolean isEnabled() {
return (m_flags & ENABLED_FLAG) == ENABLED_FLAG;
}
/**
* @return the next contact in the world's contact list
*/
public Contact getNext() {
return m_next;
}
/**
* @return the first fixture in this contact
*/
public Fixture getFixtureA() {
return m_fixtureA;
}
public int getChildIndexA() {
return m_indexA;
}
/**
* @return the second fixture in this contact
*/
public Fixture getFixtureB() {
return m_fixtureB;
}
public int getChildIndexB() {
return m_indexB;
}
public void setFriction(float friction) {
m_friction = friction;
}
public float getFriction() {
return m_friction;
}
public void resetFriction() {
m_friction = mixFriction(m_fixtureA.getFriction(), m_fixtureB.getFriction());
}
public void setRestitution(float restitution) {
m_restitution = restitution;
}
public float getRestitution() {
return m_restitution;
}
public void resetRestitution() {
m_restitution = mixRestitution(m_fixtureA.getRestitution(), m_fixtureB.getRestitution());
}
public void setTangentSpeed(float speed) {
m_tangentSpeed = speed;
}
public float getTangentSpeed() {
return m_tangentSpeed;
}
public abstract void evaluate(Manifold manifold, Transform xfA, Transform xfB);
/**
* Flag this contact for filtering. Filtering will occur the next time step.
*/
public void flagForFiltering() {
m_flags |= FILTER_FLAG;
}
// djm pooling
private final Manifold oldManifold = new Manifold();
public void update(ContactListener listener) {
oldManifold.set(m_manifold);
// Re-enable this contact.
m_flags |= ENABLED_FLAG;
boolean wasTouching = (m_flags & TOUCHING_FLAG) == TOUCHING_FLAG;
boolean sensorA = m_fixtureA.isSensor();
boolean sensorB = m_fixtureB.isSensor();
boolean sensor = sensorA || sensorB;
Body bodyA = m_fixtureA.getBody();
Body bodyB = m_fixtureB.getBody();
Transform xfA = bodyA.getTransform();
Transform xfB = bodyB.getTransform();
boolean touching;
if (sensor) {
Shape shapeA = m_fixtureA.getShape();
Shape shapeB = m_fixtureB.getShape();
touching = GenericCollision.testOverlap(pool, shapeA, m_indexA, shapeB, m_indexB, xfA, xfB);
// Sensors don't generate manifolds.
m_manifold.pointCount = 0;
} else {
evaluate(m_manifold, xfA, xfB);
touching = m_manifold.pointCount > 0;
// Match old contact ids to new contact ids and copy the
// stored impulses to warm start the solver.
for (int i = 0; i < m_manifold.pointCount; ++i) {
ManifoldPoint mp2 = m_manifold.points[i];
mp2.normalImpulse = 0.0f;
mp2.tangentImpulse = 0.0f;
ContactID id2 = mp2.id;
for (int j = 0; j < oldManifold.pointCount; ++j) {
ManifoldPoint mp1 = oldManifold.points[j];
if (mp1.id.isEqual(id2)) {
mp2.normalImpulse = mp1.normalImpulse;
mp2.tangentImpulse = mp1.tangentImpulse;
break;
}
}
}
if (touching != wasTouching) {
bodyA.setAwake(true);
bodyB.setAwake(true);
}
}
if (touching) {
m_flags |= TOUCHING_FLAG;
} else {
m_flags &= ~TOUCHING_FLAG;
}
if (listener == null) {
return;
}
if (!wasTouching && touching) {
listener.beginContact(this);
}
if (wasTouching && !touching) {
listener.endContact(this);
}
if (!sensor && touching) {
listener.preSolve(this, oldManifold);
}
}
/**
* Friction mixing law.
* The idea is to allow either fixture to drive the restitution to zero.
* For example, anything slides on ice.
*/
private static float mixFriction(float friction1, float friction2) {
return FXGLMath.sqrtF(friction1 * friction2);
}
/**
* Restitution mixing law.
* The idea is allow for anything to bounce off an inelastic surface.
* For example, a superball bounces on anything.
*/
private static float mixRestitution(float restitution1, float restitution2) {
return restitution1 > restitution2 ? restitution1 : restitution2;
}
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