com.almasb.fxgl.physics.box2d.dynamics.joints.PrismaticJointDef Maven / Gradle / Ivy

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/*
 * FXGL - JavaFX Game Library. The MIT License (MIT).
 * Copyright (c) AlmasB ([email protected]).
 * See LICENSE for details.
 */
package com.almasb.fxgl.physics.box2d.dynamics.joints;

import com.almasb.fxgl.core.math.Vec2;
import com.almasb.fxgl.physics.box2d.dynamics.Body;

/**
 * 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.
 * @author Daniel
 *
 */
public class PrismaticJointDef extends JointDef {


    /**
     * The local anchor point relative to body1's origin.
     */
    public final Vec2 localAnchorA;

    /**
     * The local anchor point relative to body2's origin.
     */
    public final Vec2 localAnchorB;

    /**
     * The local translation axis in body1.
     */
    public final Vec2 localAxisA;

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

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

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

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

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

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

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

    public PrismaticJointDef() {
        super(JointType.PRISMATIC);
        localAnchorA = new Vec2();
        localAnchorB = new Vec2();
        localAxisA = new Vec2(1.0f, 0.0f);
        referenceAngle = 0.0f;
        enableLimit = false;
        lowerTranslation = 0.0f;
        upperTranslation = 0.0f;
        enableMotor = false;
        maxMotorForce = 0.0f;
        motorSpeed = 0.0f;
    }


    /**
     * Initialize the bodies, anchors, axis, and reference angle using the world anchor and world
     * axis.
     */
    public void initialize(Body b1, Body b2, Vec2 anchor, Vec2 axis) {
        bodyA = b1;
        bodyB = b2;
        bodyA.getLocalPointToOut(anchor, localAnchorA);
        bodyB.getLocalPointToOut(anchor, localAnchorB);
        bodyA.getLocalVectorToOut(axis, localAxisA);
        referenceAngle = bodyB.getAngle() - bodyA.getAngle();
    }
}