apps: add HelloJoint

apps/src/main/java/com/github/stephengold/vsport/tutorial/HelloJoint.java

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+/*
+ Copyright (c) 2020-2023, Stephen Gold
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ 1. Redistributions of source code must retain the above copyright notice, this
+    list of conditions and the following disclaimer.
+
+ 2. Redistributions in binary form must reproduce the above copyright notice,
+    this list of conditions and the following disclaimer in the documentation
+    and/or other materials provided with the distribution.
+
+ 3. Neither the name of the copyright holder nor the names of its
+    contributors may be used to endorse or promote products derived from
+    this software without specific prior written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.github.stephengold.vsport.tutorial;
+
+import com.github.stephengold.vsport.Constants;
+import com.github.stephengold.vsport.TextureKey;
+import com.github.stephengold.vsport.input.RotateMode;
+import com.github.stephengold.vsport.physics.BasePhysicsApp;
+import com.github.stephengold.vsport.physics.ConstraintGeometry;
+import com.jme3.bullet.PhysicsSpace;
+import com.jme3.bullet.PhysicsTickListener;
+import com.jme3.bullet.RotationOrder;
+import com.jme3.bullet.collision.shapes.BoxCollisionShape;
+import com.jme3.bullet.collision.shapes.PlaneCollisionShape;
+import com.jme3.bullet.collision.shapes.SphereCollisionShape;
+import com.jme3.bullet.joints.JointEnd;
+import com.jme3.bullet.joints.New6Dof;
+import com.jme3.bullet.objects.PhysicsBody;
+import com.jme3.bullet.objects.PhysicsRigidBody;
+import com.jme3.math.Matrix3f;
+import com.jme3.math.Plane;
+import com.jme3.math.Vector3f;
+import jme3utilities.math.MyVector3f;
+import org.joml.Vector2fc;
+
+/**
+ * A simple example of a PhysicsJoint.
+ * <p>
+ * Builds upon HelloKinematics.
+ *
+ * @author Stephen Gold [email protected]
+ */
+public class HelloJoint
+        extends BasePhysicsApp<PhysicsSpace>
+        implements PhysicsTickListener {
+    // *************************************************************************
+    // constants
+
+    /**
+     * physics-space Y coordinate of the ground plane
+     */
+    final private static float groundY = -4f;
+    /**
+     * half the height of the paddle (in physics-space units)
+     */
+    final private static float paddleHalfHeight = 1f;
+    // *************************************************************************
+    // fields
+
+    /**
+     * mouse-controlled kinematic paddle
+     */
+    private static PhysicsRigidBody paddleBody;
+    /**
+     * latest ground location indicated by the mouse cursor
+     */
+    final private static Vector3f mouseLocation = new Vector3f();
+    // *************************************************************************
+    // new methods exposed
+
+    /**
+     * Main entry point for the HelloJoint application.
+     *
+     * @param arguments array of command-line arguments (not null)
+     */
+    public static void main(String[] arguments) {
+        HelloJoint application = new HelloJoint();
+        application.start();
+    }
+    // *************************************************************************
+    // BasePhysicsApp methods
+
+    /**
+     * Create the PhysicsSpace. Invoked once during initialization.
+     *
+     * @return a new instance
+     */
+    @Override
+    public PhysicsSpace createSpace() {
+        PhysicsSpace result
+                = new PhysicsSpace(PhysicsSpace.BroadphaseType.DBVT);
+
+        // To enable the callbacks, register the application as a tick listener.
+        result.addTickListener(this);
+
+        // Reduce the time step for better accuracy.
+        result.setAccuracy(0.005f);
+
+        return result;
+    }
+
+    /**
+     * Initialize the application.
+     */
+    @Override
+    public void initialize() {
+        super.initialize();
+
+        configureCamera();
+        setLightDirection(new Vector3f(7f, 3f, 5f));
+    }
+
+    /**
+     * Populate the PhysicsSpace. Invoked once during initialization.
+     */
+    @Override
+    public void populateSpace() {
+        // Add a static plane to represent the ground.
+        addPlane(groundY);
+
+        // Add a mouse-controlled kinematic paddle.
+        addPaddle();
+
+        // Add a dynamic ball.
+        PhysicsRigidBody ballBody = addBall();
+
+        // Add a single-ended physics joint to constrain the ball's motion.
+        Vector3f pivotInBall = new Vector3f(0f, 3f, 0f);
+        Vector3f pivotInWorld = new Vector3f(0f, groundY + 4f, 0f);
+        Matrix3f rotInBall = Matrix3f.IDENTITY;
+        Matrix3f rotInWorld = Matrix3f.IDENTITY;
+        New6Dof joint = new New6Dof(ballBody, pivotInBall, pivotInWorld,
+                rotInBall, rotInWorld, RotationOrder.XYZ);
+        physicsSpace.addJoint(joint);
+
+        // Visualize the physics joint.
+        new ConstraintGeometry(joint, JointEnd.B);
+    }
+
+    /**
+     * Callback invoked during each iteration of the main update loop.
+     */
+    @Override
+    public void render() {
+        // Calculate the ground location (if any) indicated by the mouse cursor.
+        Vector2fc screenXy = getInputManager().locateCursor();
+        if (screenXy != null) {
+            float nearZ = -1f;
+            Vector3f nearLocation = cam.clipToWorld(screenXy, nearZ, null);
+            float farZ = +1f;
+            Vector3f farLocation = cam.clipToWorld(screenXy, farZ, null);
+            if (nearLocation.y > groundY && farLocation.y < groundY) {
+                float dy = nearLocation.y - farLocation.y;
+                float t = (nearLocation.y - groundY) / dy;
+                MyVector3f.lerp(t, nearLocation, farLocation, mouseLocation);
+            }
+        }
+        super.render();
+    }
+    // *************************************************************************
+    // PhysicsTickListener methods
+
+    /**
+     * Callback from Bullet, invoked just before each simulation step.
+     *
+     * @param space the space that's about to be stepped (not null)
+     * @param timeStep the time per simulation step (in seconds, &ge;0)
+     */
+    @Override
+    public void prePhysicsTick(PhysicsSpace space, float timeStep) {
+        // Reposition the paddle based on the mouse location.
+        Vector3f bodyLocation = mouseLocation.add(0f, paddleHalfHeight, 0f);
+        paddleBody.setPhysicsLocation(bodyLocation);
+    }
+
+    /**
+     * Callback from Bullet, invoked just after each simulation step.
+     *
+     * @param space the space that was just stepped (not null)
+     * @param timeStep the time per simulation step (in seconds, &ge;0)
+     */
+    @Override
+    public void physicsTick(PhysicsSpace space, float timeStep) {
+        // do nothing
+    }
+    // *************************************************************************
+    // private methods
+
+    /**
+     * Create a dynamic rigid body with a sphere shape and add it to the space.
+     *
+     * @return the new body
+     */
+    private PhysicsRigidBody addBall() {
+        float radius = 0.4f;
+        SphereCollisionShape shape = new SphereCollisionShape(radius);
+
+        float mass = 0.2f;
+        PhysicsRigidBody result = new PhysicsRigidBody(shape, mass);
+        physicsSpace.addCollisionObject(result);
+
+        // Disable sleep (deactivation).
+        result.setEnableSleep(false);
+
+        visualizeShape(result);
+
+        return result;
+    }
+
+    /**
+     * Create a kinematic body with a box shape and add it to the space.
+     */
+    private void addPaddle() {
+        BoxCollisionShape shape
+                = new BoxCollisionShape(0.3f, paddleHalfHeight, 1f);
+        paddleBody = new PhysicsRigidBody(shape);
+        paddleBody.setKinematic(true);
+
+        physicsSpace.addCollisionObject(paddleBody);
+        visualizeShape(paddleBody);
+    }
+
+    /**
+     * Add a horizontal plane body to the space.
+     *
+     * @param y (the desired elevation, in physics-space coordinates)
+     */
+    private void addPlane(float y) {
+        Plane plane = new Plane(Vector3f.UNIT_Y, y);
+        PlaneCollisionShape shape = new PlaneCollisionShape(plane);
+        PhysicsRigidBody body
+                = new PhysicsRigidBody(shape, PhysicsBody.massForStatic);
+
+        physicsSpace.addCollisionObject(body);
+
+        // visualization
+        String resourceName = "/Textures/greenTile.png";
+        float maxAniso = 16f;
+        TextureKey textureKey
+                = new TextureKey("classpath://" + resourceName, maxAniso);
+        visualizeShape(body, 0.1f)
+                .setSpecularColor(Constants.DARK_GRAY)
+                .setTexture(textureKey);
+    }
+
+    /**
+     * Configure the Camera and CIP during startup.
+     */
+    private static void configureCamera() {
+        getCameraInputProcessor().setRotationMode(RotateMode.None);
+
+        cam.setLocation(new Vector3f(0f, 5f, 10f));
+        cam.setUpAngle(-0.6f);
+        cam.setAzimuth(-1.6f);
+    }
+}