How to rigidly join two RigidBody3d

This is a READ-ONLY snapshot of the Godot Community Forums when TwistedTwigleg was the owner, which is hosted for archival reasons only. The current Godot Community Forums can be found here.

Some links may point to external websites, including the current Godot Community Forums. These websites are not associated with TwistedTwigleg.

Bruma

Hello everyone.
Newbie here, so, sorry for the probably dumb question.
I'm trying to create an Apollo simulator, with real physic. Since now, all went ok: I have coded a central gravitational force and my spacecraft are orbiting the Moon.
They are controlled via applied impulse, so I can move and rotate them as the real one.
Now I would like to simulate the docking between the Lunar Modul and the Command and Service Module.
I tried with Hinge Joint and the Generic 6dof Joint. Translation are ok: apply force to the Command Module makes the Lunar module move accordingly, but the rotations are not working. Angular momentum applied to the command module does nothing, it seems to be locked by the joint. The joint has limits in angle (the need to become a solid and unique spacecraft), but limiting the joint rotation seems to limit the entire rotation. Once joined, the Command module does not rotate and so the lunar Module is not rotating too.
Here is a screenshot, hoping to clarify a bit:

Is there a better way to achieve my goals? Thank you in advance for thanking time to help me.

cybereality

You should try a pin joint.

Bruma

Thank you for the suggestion!
Unfortunately, pin joint has the same problem...
I'm now trying to do it by code, and I might be close to a solution.
I have a node 3d as a child of Command module. Once docked, I get the global position of the Lunar Module and I move the dummy in the same position. Then, I assign to the lunar module the same global position and orientation of the node 3d. If i move the Command module, the child node 3d move accordingly and drive the position and orientation of the Lunar module.
The problem is that once I undock the LEM, it has no momentum and stand still, but I'm working on it. I don't know if this is the best solution, but it seems promising. I'm still open to other point of view!

cybereality

Pin joint can lock the rotation and position, so they move as one object. Once you break the link, it should maintain the physics momentum, but I haven't tried it.

Bruma

Thank you again.
Yes, it can, but for some reasons if I lock the rotation I'm no longer able to rotate the spacecraft by applying forces as when it was not joined. I would like to propagate the inertia of the Command Module to the Lunar Module.

Megalomaniak

I guess it's a question of what are you parenting to what. In a space game and specifically a space environment I guess it would make sense to always parent the object of lesser mass-moment to the object of greater mass-moment of if that makes sense...

cybereality

That should work fine. Can you explain how you are applying forces?

Bruma

I apply forces in _physics_process using apply_central_impulse. The impulse is on 3 axes, so I can translate. Similarly, using apply_torque_impulse I can rotate the rigid body.