PrismaticJointDef.java

/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.physics.box2d.joints;

import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.JointDef;

/**
 * Prismatic joint definition. This requires defining a line of motion using an axis and an anchor point. The definition
 * uses local anchor points and a local axis so that the initial configuration can violate the constraint slightly. The
 * joint translation is zero when the local anchor points coincide in world space. Using local anchors and a local axis
 * helps when saving and loading a game.
 * 
 * @warning at least one body should by dynamic with a non-fixed rotation.
 */
public class PrismaticJointDef extends JointDef {
	public PrismaticJointDef() {
		type = JointType.PrismaticJoint;
	}

	/** Initialize the bodies, anchors, axis, and reference angle using the world anchor and world axis. */
	public void initialize(Body bodyA, Body bodyB, Vector2 anchor, Vector2 axis) {
		this.bodyA = bodyA;
		this.bodyB = bodyB;
		localAnchorA.set(bodyA.getLocalPoint(anchor));
		localAnchorB.set(bodyB.getLocalPoint(anchor));
		localAxisA.set(bodyA.getLocalVector(axis));
		referenceAngle = bodyB.getAngle() - bodyA.getAngle();

	}

	/** The local anchor point relative to body1's origin. */
	public final Vector2 localAnchorA = new Vector2();

	/** The local anchor point relative to body2's origin. */
	public final Vector2 localAnchorB = new Vector2();

	/** The local translation axis in body1. */
	public final Vector2 localAxisA = new Vector2(1, 0);

	/** The constrained angle between the bodies: body2_angle - body1_angle. */
	public float referenceAngle = 0;

	/** Enable/disable the joint limit. */
	public boolean enableLimit = false;

	/** The lower translation limit, usually in meters. */
	public float lowerTranslation = 0;

	/** The upper translation limit, usually in meters. */
	public float upperTranslation = 0;

	/** Enable/disable the joint motor. */
	public boolean enableMotor = false;

	/** The maximum motor torque, usually in N-m. */
	public float maxMotorForce = 0;

	/** The desired motor speed in radians per second. */
	public float motorSpeed = 0;
}