kotlin-apps: add the HelloCharacter app

kotlin-apps/build.gradle

@@ -52,6 +52,10 @@ tasks.register('HelloCcd', JavaExec) {
     description = 'Runs the Kotlin version of the HelloCcd tutorial app.'
     mainClass = 'com.github.stephengold.lbjexamples.ktapps.HelloCcdKt'
 }
+tasks.register('HelloCharacter', JavaExec) {
+    description = 'Runs the Kotlin version of the HelloCharacter tutorial app.'
+    mainClass = 'com.github.stephengold.lbjexamples.ktapps.HelloCharacterKt'
+}
 tasks.register('HelloContactResponse', JavaExec) {
     description = 'Runs the Kotlin version of the HelloContactResponse tutorial app.'
     mainClass = 'com.github.stephengold.lbjexamples.ktapps.HelloContactResponseKt'

kotlin-apps/src/main/kotlin/com/github/stephengold/lbjexamples/ktapps/HelloCharacter.kt

@@ -0,0 +1,171 @@
+/*
+ Copyright (c) 2024 Stephen Gold and Yanis Boudiaf
+
+ 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.lbjexamples.ktapps
+
+import com.github.stephengold.sport.Constants
+import com.github.stephengold.sport.input.RotateMode
+import com.github.stephengold.sport.physics.BasePhysicsApp
+import com.jme3.bullet.PhysicsSpace
+import com.jme3.bullet.PhysicsTickListener
+import com.jme3.bullet.collision.shapes.Box2dShape
+import com.jme3.bullet.collision.shapes.CapsuleCollisionShape
+import com.jme3.bullet.objects.PhysicsBody
+import com.jme3.bullet.objects.PhysicsCharacter
+import com.jme3.bullet.objects.PhysicsRigidBody
+import com.jme3.math.FastMath
+import com.jme3.math.Quaternion
+import com.jme3.math.Vector3f
+
+/*
+ * A simple example of character physics.
+ *
+ * Builds upon HelloStaticBody.
+ *
+ * author:  Stephen Gold [email protected]
+ */
+
+/*
+ * Main entry point for the HelloCharacter application.
+ */
+fun main() {
+    val application = HelloCharacter()
+    application.start()
+}
+
+/*
+ * character being tested
+ */
+var character: PhysicsCharacter? = null
+
+class HelloCharacter : BasePhysicsApp<PhysicsSpace>(), PhysicsTickListener {
+    // *************************************************************************
+    // BasePhysicsApp functions
+
+    /*
+     * Create the PhysicsSpace. Invoked once during initialization.
+     */
+    override fun createSpace(): PhysicsSpace {
+        val result = configurePhysics()
+        return result
+    }
+
+    /*
+     * Initialize the application.
+     */
+    override fun initialize() {
+        super.initialize()
+
+        getCameraInputProcessor().setRotationMode(RotateMode.DragLMB)
+        setBackgroundColor(Constants.SKY_BLUE)
+    }
+
+    /*
+     * Populate the PhysicsSpace. Invoked once during initialization.
+     */
+    override fun populateSpace() {
+        // Create a character with a capsule shape and add it to the space.
+        val capsuleRadius = 0.5f
+        val capsuleHeight = 1f
+        val shape = CapsuleCollisionShape(capsuleRadius, capsuleHeight)
+        val stepHeight = 0.01f
+        character = PhysicsCharacter(shape, stepHeight)
+        physicsSpace.addCollisionObject(character)
+
+        // Add a square to represent the ground.
+        val halfExtent = 4f
+        val y = -2f
+        val ground = addSquare(halfExtent, y)
+
+        // Visualize both physics objects.
+        visualizeShape(character)
+        visualizeShape(ground)
+    }
+    // *************************************************************************
+    // PhysicsTickListener functions
+
+    /*
+     * Callback from Bullet, invoked just before each simulation step.
+     *
+     * space:  the space that's about to be stepped (not null)
+     * timeStep:  the duration of the simulation step (in seconds, >=0)
+     */
+    override fun prePhysicsTick(space: PhysicsSpace, timeStep: Float) {
+        // If the character is touching the ground, cause it to jump.
+        if (character!!.onGround()) {
+            character!!.jump()
+        }
+    }
+
+    /*
+     * Callback from Bullet, invoked just after each simulation step.
+     *
+     * space:  the space that was just stepped (not null)
+     * timeStep:  the duration of the simulation step (in seconds, >=0)
+     */
+    override fun physicsTick(space: PhysicsSpace, timeStep: Float) {
+        // do nothing
+    }
+    // *************************************************************************
+    // private functions
+
+    /*
+     * Add a horizontal square body to the space.
+     *
+     * halfExtent:  half of the desired side length
+     * y:  the desired elevation, in physics-space coordinates
+     */
+    private fun addSquare(halfExtent: Float, y: Float): PhysicsRigidBody {
+        // Construct a static rigid body with a square shape.
+        val shape = Box2dShape(halfExtent)
+        val result = PhysicsRigidBody(shape, PhysicsBody.massForStatic)
+
+        physicsSpace.addCollisionObject(result)
+
+        // Rotate it 90 degrees to a horizontal orientation.
+        val rotate90 = Quaternion().fromAngles(-FastMath.HALF_PI, 0f, 0f)
+        result.setPhysicsRotation(rotate90)
+
+        // Translate it to the desired elevation.
+        result.setPhysicsLocation(Vector3f(0f, y, 0f))
+
+        return result
+    }
+
+    /*
+     * Configure physics during startup.
+     */
+    private fun configurePhysics(): PhysicsSpace {
+        val result = PhysicsSpace(PhysicsSpace.BroadphaseType.DBVT)
+
+        // To enable the callbacks, register the application as a tick listener.
+        result.addTickListener(this)
+
+        return result
+    }
+}