Hi.
I’m making a 3D game with moving along X and Y axis and not Z. So it is possible to lock this Z axis? I’m using Bullet.
Regards
You mean constraining the physics behavior on X & Y axis only?
Once I asked the same question and @normen said native bullet can do that. Now we have it. So, the answer is ‘yes’.
@iamcreasy, thanks for reply. So I can do it. My next question is: how? 
Creasy’s conclusion isn’t quite right, you can only lock the rotation completely.
@normen translation can’t be constrained? 
Lol, constraining translation and rotation is called “kinematic mode” 
1 Like
Yeah, but i don’t want to lock translation and rotation, but only translation in Z axis…
The only way I can think of right now is setting the angular velocity for Z to 0 on each physics tick but I didn’t test that…
1 Like
Yeah @douter, thats about the only way, though people have reported issues when doing it like that (drifting). Would be cool if you could report back.
Yeah, but i don’t want to lock translation and rotation, but only translation in Z axis…
Originally by @normen:
you can only lock the rotation completely.
It means you can't lock only one axis, but x, y and z.
So i can’t lock Z axis completely? :<
Did you try if what douter said works for you?
Yeah, but my problem is: rotating. My object is rotating along Z axis…
Edit:
Ah, i did something wrongly. I’ll test something…
Edit2:
Not works :<
[java] Vector3f omg = orbPhys.getAngularVelocity();
omg.z = 0;
orbPhys.setAngularVelocity(omg);[/java]
In simpleUpdate()… Maybe i’m doing something wrongly again? 
My object (ball) is rotating and moving, but O-M-G-very-slooow…
Does this work?
[java]import com.jme3.bullet.PhysicsSpace;
import com.jme3.bullet.PhysicsTickListener;
import com.jme3.bullet.control.RigidBodyControl;
import com.jme3.math.Vector3f;
public class ZLockControl extends RigidBodyControl implements PhysicsTickListener {
public ZLockControl(float mass) {
super(mass);
}
@Override
public void setPhysicsSpace(PhysicsSpace space) {
super.setPhysicsSpace(space);
space.addTickListener(this);
}
@Override
public void prePhysicsTick(PhysicsSpace space, float f) {
setAngularVelocity(Vector3f.ZERO);
}
@Override
public void physicsTick(PhysicsSpace space, float f) {
}
}[/java]
1 Like
Looks good. For good measure you should remove the listener before calling super.setPhysicsSpace() if space == null
1 Like
No, the object is moving slowly again…
lag?
No, the object is moving slowly again…
Hm, try doing it post physics tick too..
As far as I understand you want to constrain the object from moving in the z direction, so why people are mentioning rotation I don’t understand. Edit: Since you’re mentioning axis, although later you mention moving in x and y direction.
[java]
import com.jme3.bullet.PhysicsSpace;
import com.jme3.bullet.PhysicsTickListener;
import com.jme3.bullet.control.RigidBodyControl;
import com.jme3.math.Vector3f;
public class ZLockControl extends RigidBodyControl implements PhysicsTickListener {
Vector3f linearVelocityVector;
public ZLockControl(float mass) {
super(mass);
}
@Override
public void setPhysicsSpace(PhysicsSpace space) {
super.setPhysicsSpace(space);
space.addTickListener(this);
}
@Override
public void prePhysicsTick(PhysicsSpace space, float f) {
linearVelocityVector = getLinearVelocity();
linearVelocityVector.z = 0;
setLinearVelocity(linearVelocityVector);
}
@Override
public void physicsTick(PhysicsSpace space, float f) {
}
}
[/java]
1 Like
I guessed he wanted 2d physics which mostly means no rotation around the x axis… What you do there is bad voodoo btw, do not get().set() at any time in jme3!
1 Like