👦 📐 🤦🏾 永久移动 ☁️ 🐭 👢

尊敬的用户habr.com，下午好！这是该主题的第三篇文章。我整天工作，我无法离开惊人的Box2D库。

如果您还没有阅读第一篇和第二篇文章，请务必仔细阅读，这将很有趣！我在Eclipse中工作，在Java中编写。我为什么这么称呼我的文章？继续阅读-很快一切都会变得清晰起来！剧透：我们将制造自己的永动机（包括汽车），也许我们会自己制造机器！

图1.永动机。

因此，今天我们将尝试获得以下内容：

图2.带引擎的机器。

是的，这不是错字！今天，我们将制造一台具有真实发动机的机器，这与真实发动机是无法区分的！这不是第一篇文章为您提供的“购物车”。

有关连接libGDX的信息，请参阅第一篇文章。

这是显示我的装配体外观的图片。我将带有Constants类的Utils包添加到Core文件夹，该文件夹仅包含一个常数-每米的像素数。这样一来，世界就不再庞大。

图3.我的构建。

这是来自com.mygdx.game.desktop的DesktopLauncher类的代码：

将此代码粘贴到类中，然后将其忽略。

package com.mygdx.game.desktop; import com.badlogic.gdx.backends.lwjgl.LwjglApplication; import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration; import com.mygdx.game.MyGdxGame; public class DesktopLauncher { public static void main(String[] arg) { LwjglApplicationConfiguration config = new LwjglApplicationConfiguration(); //   config.width = 720; //   config.height = 480; config.backgroundFPS = 60; config.foregroundFPS = 60; new LwjglApplication(new MyGdxGame(), config); } }

以下MyGdxGame类的代码来自com.mygdx.game包。一切都在代码注释中。

我们创造世界和机器。

 package com.mygdx.game; import com.badlogic.gdx.ApplicationAdapter; import com.badlogic.gdx.Gdx; import com.badlogic.gdx.Input.Keys; import com.badlogic.gdx.graphics.GL20; import com.badlogic.gdx.graphics.OrthographicCamera; import com.badlogic.gdx.math.Vector2; import com.badlogic.gdx.math.Vector3; import com.badlogic.gdx.physics.box2d.Body; import com.badlogic.gdx.physics.box2d.BodyDef; import com.badlogic.gdx.physics.box2d.Box2DDebugRenderer; import com.badlogic.gdx.physics.box2d.CircleShape; import com.badlogic.gdx.physics.box2d.FixtureDef; import com.badlogic.gdx.physics.box2d.PolygonShape; import com.badlogic.gdx.physics.box2d.World; import com.badlogic.gdx.physics.box2d.joints.RevoluteJointDef; import utils.Constants; public class MyGdxGame extends ApplicationAdapter { private OrthographicCamera camera; private boolean DEBUG = false; private World world; private Box2DDebugRenderer b2dr; //  private Body box; //   private Body backweel; //   private Body frontweel; private Body floor; private Body triangle; //   private float m = -20; public void create() { float w = Gdx.graphics.getWidth(); float h = Gdx.graphics.getHeight(); camera = new OrthographicCamera(); camera.setToOrtho(false, w / 2, h / 2); world = new World(new Vector2(0, -9.8f), false); b2dr = new Box2DDebugRenderer(); //   floor = createFloor(); //   triangle = createTriangle(20f, 40f, 30f, -2f, -2f, 5f); triangle = createTriangle(50f, 60f, 80f, -2f, 10f, -2f); triangle = createTriangle(100f, 160f, 200f, -2f, 20f, -2f); triangle = createTriangle(280f, 290f, 300f, -2f, 100f, -2f); //   box = createBox(); //   backweel = createWeel(-1f, 2f); frontweel = createWeel(4.5f, 2f); //        connected(); } //      public void connected() { revJoint(box, backweel, -1f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); revJoint(box, frontweel, 4.5f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); } //   !  ! public void revJoint(Body body1, Body body2, float xo, float yo) { //   RevoluteJointDef rjd = new RevoluteJointDef(); //    rjd.enableMotor = true; //  .      ,  ,  //  .    .   -   ! rjd.motorSpeed = m; //   rjd.maxMotorTorque = 30; rjd.collideConnected = false; rjd.bodyA = body1; rjd.bodyB = body2; rjd.localAnchorA.set(xo, yo); world.createJoint(rjd); } public void render() { update(Gdx.graphics.getDeltaTime()); Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); b2dr.render(world, camera.combined.scl(Constants.PPM)); } public void resize(int width, int height) { camera.setToOrtho(false, width / 2, height / 2); } public void dispose() { world.dispose(); b2dr.dispose(); } public void update(float delta) { world.step(1 / 60f, 6, 2); cameraUpdate(delta); inputUpdate(delta); } //       ,     public void inputUpdate(float delta) { if (Gdx.input.isKeyPressed(Keys.SPACE)) { box.setLinearVelocity(5, 5); } } //     public void cameraUpdate(float delta) { Vector3 position = camera.position; position.x = box.getPosition().x * Constants.PPM; position.y = box.getPosition().y * Constants.PPM; camera.position.set(position); camera.update(); } //     public Body createBox() { Vector2[] verticles = new Vector2[8]; verticles[0] = new Vector2(2f * 10 / utils.Constants.PPM, 2f * 10 / utils.Constants.PPM); verticles[1] = new Vector2(2f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); verticles[2] = new Vector2(-2f * 10 / utils.Constants.PPM, 2f * 10 / utils.Constants.PPM); verticles[3] = new Vector2(-2f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); verticles[4] = new Vector2(6f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); verticles[5] = new Vector2(6f * 10 / utils.Constants.PPM, 0f * 10 / utils.Constants.PPM); verticles[6] = new Vector2(-1f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); verticles[7] = new Vector2(4.5f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); PolygonShape shape = new PolygonShape(); Body fBody; BodyDef def = new BodyDef(); def.type = BodyDef.BodyType.DynamicBody; def.position.set(0, 0); def.fixedRotation = false; fBody = world.createBody(def); shape.set(verticles); //    FixtureDef fd = new FixtureDef(); // ,     fd.shape = shape; //   fd.friction = 0.5f; //   fd.density = 3f; //   fd.restitution = 0.5f; fBody.createFixture(fd); fBody.createFixture(fd); shape.dispose(); return fBody; } //   public Body createWeel(float xo, float yo) { CircleShape shape = new CircleShape(); Body fBody; BodyDef def = new BodyDef(); def.type = BodyDef.BodyType.DynamicBody; def.position.set(xo * 10 / utils.Constants.PPM, yo * 10 / utils.Constants.PPM); def.fixedRotation = false; fBody = world.createBody(def); shape.setRadius(2.0f * 10 / utils.Constants.PPM); //    FixtureDef fd = new FixtureDef(); fd.shape = shape; fd.friction = 0.7f; fd.density = 3f; fd.restitution = 0.5f; fBody.createFixture(fd); shape.dispose(); return fBody; } //   public Body createFloor() { Vector2[] verticles = new Vector2[4]; verticles[0] = new Vector2(-100f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); verticles[1] = new Vector2(300f * 10 / utils.Constants.PPM, -2f * 10 / utils.Constants.PPM); verticles[2] = new Vector2(300f * 10 / utils.Constants.PPM, -5f * 10 / utils.Constants.PPM); verticles[3] = new Vector2(-100f * 10 / utils.Constants.PPM, -5f * 10 / utils.Constants.PPM); PolygonShape shape = new PolygonShape(); Body fBody; BodyDef def = new BodyDef(); def.type = BodyDef.BodyType.StaticBody; def.position.set(0, 0); def.fixedRotation = true; fBody = world.createBody(def); shape.set(verticles); FixtureDef fd = new FixtureDef(); fd.shape = shape; fd.friction = 0.5f; fd.density = 3f; fd.restitution = 0.5f; fBody.createFixture(fd); shape.dispose(); return fBody; } //    ! public Body createTriangle(float xo, float x1, float x2, float yo, float y1, float y2) { Vector2[] verticles = new Vector2[3]; verticles[0] = new Vector2(xo * 10 / utils.Constants.PPM, yo * 10 / utils.Constants.PPM); verticles[1] = new Vector2(x1 * 10 / utils.Constants.PPM, y1 * 10 / utils.Constants.PPM); verticles[2] = new Vector2(x2 * 10 / utils.Constants.PPM, y2 * 10 / utils.Constants.PPM); PolygonShape shape = new PolygonShape(); Body fBody; BodyDef def = new BodyDef(); def.type = BodyDef.BodyType.StaticBody; def.position.set(0, 0); def.fixedRotation = true; fBody = world.createBody(def); shape.set(verticles); FixtureDef fd = new FixtureDef(); fd.shape = shape; fd.friction = 0.5f; fd.density = 10f; fd.restitution = 0f; fBody.createFixture(fd); shape.dispose(); return fBody; } }

图4.编译时会得到什么？

我们为汽车制造一个使车轮旋转的电动机。但这是永远有效的，因为没有能量损失。因此，我们创建了永动机！

而且您想知道该课程的结尾是什么？您可以随时在评论中发送屏幕截图。感谢您阅读本文的结尾！希望您可以在Box2D中创建自己的汽车！

附言：我期待您在评论中的提问！游戏物理学万岁！

永久移动

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