libgdx学习记录18——Box2d物理引擎

时间：2023-11-14 09:22:20

libgdx封装了Box2D物理引擎，通过这个引擎能够模拟物理现实，使设计出的游戏更具有真实感。

libgdx中，Box2d程序的大概过程：

1. 创建物理世界world，并设置重力加速度。

2. 创建正交相机，并设置其宽高。Box2d中使用物理世界中米作为单位，而不是图像中的像素，通常设一个比值，这里为了方便，直接设置为10。

3. 创建世界中的动态物体（一般是方块、圆环或其他形状物体）和静态物体（主要指地面、墙壁等）。

4. 在渲染函数中添加world时间布，并利用DebugRenderer将添加的物体绘制出来即可。

具体代码实例：

 package com.fxb.newtest;

 import com.badlogic.gdx.ApplicationAdapter;

 import com.badlogic.gdx.Gdx;

 import com.badlogic.gdx.graphics.GL10;

 import com.badlogic.gdx.graphics.OrthographicCamera;

 import com.badlogic.gdx.graphics.glutils.ShapeRenderer;

 import com.badlogic.gdx.math.Vector2;

 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.Fixture;

 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.BodyDef.BodyType;

 public class Lib018_Box2d extends ApplicationAdapter{

     World world;

     OrthographicCamera camera;

     Box2DDebugRenderer debugRenderer;

     ShapeRenderer rend;

     @Override

     public void create() {

         // TODO Auto-generated method stub

         super.create();

         world = new World( new Vector2( 0, -10f ), true );

         debugRenderer =new Box2DDebugRenderer();

         camera = new OrthographicCamera();

         camera.setToOrtho( false, Gdx.graphics.getWidth()/10, Gdx.graphics.getHeight()/10 );

         ////create the body of box

         BodyDef boxBodyDef = new BodyDef();

         boxBodyDef.type = BodyType.DynamicBody;

         //boxBodyDef.position.x = -24 + (float)(Math.random() * 48);

         //boxBodyDef.position.y = 10 + (float)(Math.random() * 100);

         boxBodyDef.position.set( 40, 50 );

         Body boxBody = world.createBody(boxBodyDef);

         PolygonShape boxPoly = new PolygonShape();

         boxPoly.setAsBox(2, 1);

         boxBody.createFixture(boxPoly, 1);

         boxPoly.dispose();

         /////create the body of circle

         BodyDef bodyDef = new BodyDef();

         bodyDef.type = BodyType.DynamicBody;

         bodyDef.position.set( 60, 100 );

         Body bodyCircle = world.createBody( bodyDef );

         CircleShape circle = new CircleShape();

         circle.setRadius( 2 );

         FixtureDef fixtureDef = new FixtureDef();

         fixtureDef.shape = circle;

         fixtureDef.density = 1f;

         fixtureDef.friction = 0.4f;

         //fixtureDef.restitution = 0.6f;

         bodyCircle.createFixture( fixtureDef );

         circle.dispose();

         /////create the body of ground, static body, can't move

         BodyDef groundBodyDef = new BodyDef();

         groundBodyDef.type = BodyType.StaticBody;

         groundBodyDef.angle = (float)Math.PI*15/180;

         groundBodyDef.position.set( 0, 0 );

         Body groundBody = world.createBody( groundBodyDef );

         PolygonShape groundBox = new PolygonShape();

         groundBox.setAsBox( camera.viewportWidth+5, 0.5f );

         groundBody.createFixture( groundBox, 0.0f );

         groundBox.dispose();

     }

     @Override

     public void render() {

         // TODO Auto-generated method stub

         super.render();

         //Gdx.gl.glClearColor( 1, 1, 1, 0.2f );

         Gdx.gl.glClear( GL10.GL_COLOR_BUFFER_BIT );

         world.step( Gdx.graphics.getDeltaTime(), 6, 2 );

         camera.update();

         debugRenderer.render( world, camera.combined );

     }

     @Override

     public void dispose() {

         // TODO Auto-generated method stub

         debugRenderer.dispose();

         world.dispose();

         super.dispose();

     }

 }

运行结果：

libgdx学习记录18——Box2d物理引擎

程序中，添加了方块、圆环和地面三个物体，前两个为动态，地面为静态，让地面倾斜15度。

方块和圆环从高空下落到斜坡时，就向下滑动，与我们平常生活常识相吻合。

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