Hello everyone. Today I was trying some stuff and I wasn’t able to receive collision events by using a PhysicsCollisionListener.
After making a simple program to debug the problem I found what was going on.
In the following example I make two spheres collide, the simulation looks good, however the collision listener is not called. If I change the collision shape to a box, the collision is detected and the listener is called.
I thought only mesh to mesh collision wouldn’t work (and wouldn’t work at all). Is the sphere shape simply a mesh?
How can bullet run the physics simulation fine but fail to publish the event?
import com.jme3.app.Application;
import com.jme3.app.SimpleApplication;
import com.jme3.app.state.AbstractAppState;
import com.jme3.app.state.AppStateManager;
import com.jme3.bullet.BulletAppState;
import com.jme3.bullet.PhysicsSpace;
import com.jme3.bullet.collision.PhysicsCollisionEvent;
import com.jme3.bullet.collision.PhysicsCollisionListener;
import com.jme3.bullet.collision.shapes.SphereCollisionShape;
import com.jme3.bullet.control.RigidBodyControl;
import com.jme3.material.Material;
import com.jme3.math.ColorRGBA;
import com.jme3.math.Vector3f;
import com.jme3.scene.Geometry;
import com.jme3.scene.Spatial;
import com.jme3.scene.shape.Sphere;
public class CollisionTest extends SimpleApplication {
public static void main(String[] args) {
new CollisionTest().start();
}
@Override
public void simpleInitApp() {
BulletAppState bulletState = new BulletAppState();
bulletState.setDebugEnabled(true);
stateManager.attach(bulletState);
stateManager.attach(new State());
}
private class State extends AbstractAppState {
private Spatial ball1Spatial;
private Spatial ball2Spatial;
private Float counter = 0f;
@Override
public void initialize(AppStateManager stateManager, Application app) {
super.initialize(stateManager, app);
space().addCollisionListener(new CollisionListener());
ball1Spatial = createBall();
ball2Spatial = createBall();
resetBalls();
}
@Override
public void update(float tpf) {
counter += tpf;
if (counter > 1) {
counter = 0f;
resetBalls();
}
}
public Spatial createBall() {
Spatial ball = new Geometry("ball", new Sphere(8, 8, 1));
Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
mat.setColor("Color", ColorRGBA.Blue);
ball.setMaterial(mat);
// The Sphere doesn't register collisions?
ball.addControl(new RigidBodyControl(new SphereCollisionShape(1), 1));
// But Box works just fine!
// ball.addControl(new RigidBodyControl(new BoxCollisionShape(Vector3f.UNIT_XYZ)));
rootNode.attachChild(ball);
space().add(ball);
return ball;
}
public void resetBalls() {
moveTo(ball1Spatial, new Vector3f(-5, 2, 0));
push(ball1Spatial, Vector3f.UNIT_X);
moveTo(ball2Spatial, new Vector3f(5, 2, 0));
push(ball2Spatial, Vector3f.UNIT_X.negate());
}
public void moveTo(Spatial ball, Vector3f loc) {
RigidBodyControl body = ball.getControl(RigidBodyControl.class);
body.setPhysicsLocation(loc);
body.clearForces();
body.setLinearVelocity(Vector3f.ZERO);
}
public void push(Spatial ball, Vector3f dir) {
ball.getControl(RigidBodyControl.class).applyImpulse(dir.mult(50f), Vector3f.ZERO);
}
public PhysicsSpace space() {
return stateManager.getState(BulletAppState.class).getPhysicsSpace();
}
}
private class CollisionListener implements PhysicsCollisionListener {
@Override
public void collision(PhysicsCollisionEvent event) {
System.out.println("When two worlds collide!");
}
}
}
). Possibly I have an old version of the SDK.