为什么这个简单的 Box2D 东西不起作用？

Question

当我运行这个时，什么也没有发生。方块停留在 (10.0,-10.0) 并且不会掉落。为什么？

这是我的代码：

import processing.core.PApplet;
import org.jbox2d.collision.shapes.PolygonShape;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.BodyDef;
import org.jbox2d.dynamics.FixtureDef;
import org.jbox2d.dynamics.World;  

public class PhysicsWorld extends PApplet {
    
    private World world;
    private Body block;
    private static final float RATIO = 30f;
    
    public void createWorld() {
        Vec2 gravity = new Vec2(0.f,-9.8f);
        world = new World(gravity, true);
        world.setGravity(gravity);
        
    }
    
    private void createBlock(){
        BodyDef blockDef;
        PolygonShape blockShape;
        
        blockDef = new BodyDef();
        blockDef.position.set(300.f / RATIO, -300.f / RATIO);
        
        blockShape = new PolygonShape();
        blockShape.setAsBox(20/RATIO, 25/RATIO);
        
        FixtureDef fixtureDef = new FixtureDef();
        fixtureDef.shape = blockShape;
        fixtureDef.density = 1.0f;
        fixtureDef.friction = 0.8f;
        fixtureDef.restitution = 0.3f;
        
        block = world.createBody(blockDef);
        block.createFixture(fixtureDef);
    }
    
    public void setup(){
        createWorld();
        createBlock();
    }
    
    public void draw(){
        world.step(1/60, 8, 3);
        //world.clearForces();
        System.out.println(block.getPosition() +" " + world.getGravity());
        
    }

}

Answer 1

默认情况下，主体是静态的，因此只需将主体类型设置为 b2_dynamicBody 即可。