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’.
Creasy’s conclusion isn’t quite right, you can only lock the rotation completely.
Lol, constraining translation and rotation is called “kinematic mode” 
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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…
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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]
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Looks good. For good measure you should remove the listener before calling super.setPhysicsSpace() if space == null
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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]
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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!
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