Objects with no friction and no damping still slowing down

Troubleshooting physics
1

When trying to make objects floating in space, the objects still slow down and stop. Is there something I have missed?



As as simple example I added this to the standard new project:

[java]

stateManager.attach(new BulletAppState());

stateManager.getState(BulletAppState.class).getPhysicsSpace().setGravity(Vector3f.ZERO);

geom.addControl(new RigidBodyControl(1f));

geom.getControl(RigidBodyControl.class).setDamping(0f, 0f);

geom.getControl(RigidBodyControl.class).setFriction(0f);

geom.getControl(RigidBodyControl.class).applyCentralForce(Vector3f.UNIT_Y);

stateManager.getState(BulletAppState.class).getPhysicsSpace().add(geom);

[/java]



Full example:

[java]

package mygame;



import com.jme3.app.SimpleApplication;

import com.jme3.bullet.BulletAppState;

import com.jme3.bullet.control.RigidBodyControl;

import com.jme3.material.Material;

import com.jme3.math.ColorRGBA;

import com.jme3.math.Vector3f;

import com.jme3.renderer.RenderManager;

import com.jme3.scene.Geometry;

import com.jme3.scene.shape.Box;



public class Main extends SimpleApplication {



public static void main(String[] args) {

Main app = new Main();

app.start();

}



@Override

public void simpleInitApp() {

Box b = new Box(Vector3f.ZERO, 1, 1, 1);

Geometry geom = new Geometry("Box", b);



Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");

mat.setColor("Color", ColorRGBA.Blue);

geom.setMaterial(mat);



rootNode.attachChild(geom);



stateManager.attach(new BulletAppState());

stateManager.getState(BulletAppState.class).getPhysicsSpace().setGravity(Vector3f.ZERO);

geom.addControl(new RigidBodyControl(1f));

geom.getControl(RigidBodyControl.class).setDamping(0f, 0f);

geom.getControl(RigidBodyControl.class).setFriction(0f);

geom.getControl(RigidBodyControl.class).applyCentralForce(Vector3f.UNIT_Y);

stateManager.getState(BulletAppState.class).getPhysicsSpace().add(geom);





}



}

[/java]

2

It seems it only happens when the velocity is below a certain magnitude. Any idea why?

3

Don’t know but maybe setSleepingThreshold is what you need, described here:

https://wiki.jmonkeyengine.org/legacy/doku.php/jme3:advanced:physics

4

Ah, thanks for that. The default for linear movement seems to be 0.8. Setting it to zero makes things move as they should.