碰撞后如何使两个物体粘在一起?

2022-01-12 00:00:00 box2d java libgdx jbox2d

我真的被困在这我可以成功检测到碰撞，但我不能让参与碰撞的两个物体粘在一起.

I am really stuck on this I can successfully detect a collision but I can't make the two bodies involved in the collision to stick.

这是我的ContactListener

world.setContactListener(listener);

    listener = new ContactListener() {

        @Override
        public void preSolve(Contact contact, Manifold oldManifold) {

        }


        @Override
        public void postSolve(Contact contact, ContactImpulse impulse) {

        }

        //called when two fixtures cease to touch
        @Override
        public void endContact(Contact contact) {
            Fixture fixtureA = contact.getFixtureA();
            Fixture fixtureB = contact.getFixtureB();
            Gdx.app.log("beginContact", "between" + fixtureA.toString() + "and" + fixtureB.toString());
        }

        //called when two fixtures begin to touch
        @Override
        public void beginContact(Contact contact) {
            Fixture fixtureA = contact.getFixtureA();
            Fixture fixtureB = contact.getFixtureB();
            Gdx.app.log("beginContact", "between" + fixtureA.toString() + "and" + fixtureB.toString());
        }
    };

这也是我直接在 world.step() 行之后放入我的 render() 的内容

Also this is what I put in my render() straight after the world.step() line

int numContacts = world.getContactCount();

    if(numContacts > 0)
    {
        Gdx.app.log("contact", "start of contact list");
        for(Contact contact: world.getContactList())
        {
            Fixture fixtureA = contact.getFixtureA();
            Fixture fixtureB = contact.getFixtureB();
            Gdx.app.log("contact", "between" + fixtureA.toString() + "and" + fixtureB.toString());
        }
        Gdx.app.log("contact", "end of contact list");
    }

我非常困惑于解决后或预解决的问题.我跟着 iforce2d 粘弹 http://www.iforce2d.net/b2dtut/sticky-projectiles 但我不懂 C++，而且在 Eclipse 中工作时遇到很多语法错误.请有人给我看一个工作碰撞的示例代码，请在java中碰撞后身体粘在一起.

I am extremely stuck on what to put on post solve or pre-solve really confused. I followed the iforce2d sticky projectiles http://www.iforce2d.net/b2dtut/sticky-projectiles but I don't understand C++ and i get a lot of syntax errors when working in eclipse. Please can someone show me an example code of a working collision where bodies stick together after colliding in java please.

推荐答案

这就是你如何创建一个 WeldJoint 与 libgdx 包装器:

This is how you create a WeldJoint with the libgdx wrapper:

WeldJointDef wd = new WeldJointDef();
wd.bodyA = body1;
wd.bodyB = body2;
wd.referenceAngle = wd.bodyB.getAngle() - wd.bodyA.getAngle();
world.createJoint( wd );

不要尝试在 ContactListener 中创建关节.将要粘合的物体添加到列表中，并在 world.step 之后检查它们.

Do not try to create Joints inside the ContactListener. Add the bodies to be glued to a list and check them just after world.step.

好的，就像在 iforce2d 教程中一样，创建一个包含 2 个主体的对象:

Ok, like in the iforce2d tutorial,create an object to contain 2 bodies:

public class StickyInfo{
    Body bodyA;
    Body bodyB;
    public StickyInfo(Body bodyA, Body bodyB){
        this.bodyA = bodyA;
        this.bodyB = bodyB;
    }
};

然后创建一个 libgdx 数组 StickyInfo 的

Then create a libgdx Array of StickyInfo's

Array<StickyInfo> collisionsToMakeSticky = new Array<StickyInfo>();

当物体发生碰撞时(嗯，从技术上讲，它们的固定装置)，将它们添加到此列表中:

When the bodies collide (well, technically their fixtures), add them to this list:

collisionsToMakeSticky.add(new StickyInfo(body1, body2))

然后在 world.step 之后，如果 Array 不为空.创建焊接接头:

And then just after world.step, if the Array is not empty. Create the WeldJoints:

while(collisionsToMakeSticky.size>0){
    StickyInfo si = collisionsToMakeSticky.removeIndex(0);
    //Make the WeldJoint with the bodies si.bodyA and si.bodyB
}

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