Non-Springy Configurable Joint

Questions & Answers
1

I'm using configurable joint to connect two rigidbodies. My code is :

ConfigurableJoint joint = parent.AddComponent<ConfigurableJoint>();
joint.anchor = new Vector3(0, 0, 0);
joint.xMotion = ConfigurableJointMotion.Locked;
joint.yMotion = ConfigurableJointMotion.Locked;
joint.zMotion = ConfigurableJointMotion.Locked;
joint.angularXMotion = ConfigurableJointMotion.Locked;
joint.angularYMotion = ConfigurableJointMotion.Locked;
joint.angularZMotion = ConfigurableJointMotion.Locked;
joint.targetPosition = new Vector3(0, 0, 0);
joint.connectedBody = child.rigidbody;

This joint just behaves like a spring joint. I want to make it less springy or totally fixed.(I know the fixed joint but later i'll free some of the angular and linear motions)

4

You can try a combination of these

a) Set a higher physics framerate. In 'Edit/Project settings/Time/Fixed timestep" set this to a smaller value. This will increase stability and 'strength' while also being potentially a lot slower. 'FixedUpdate' will be called more often also. So be careful

b) Set the physics body iterations to a higher value. In 'Edit/Project settings/Physics/Solver Iteration Count" to something higher. This causes bodies to be more accurate with joints and in general. It helps with 'sponginess' on collisions too I think. 'FixedUpdate' will not be effected by this setting. All jointed bodies I think take on the highest connected bodies iteration count. This also can slow things slow a lot so keep an eye on the profiler. This is a global setting, but you can also selectively set body iterations individually in code. eg rigidBody.solverIterationCount = 10;

2

As far as I'm aware, there will always be some springyness, even in fixed joints and config joints which have all locks applied. This seems to be an inherent symptom and limitation of the type of physics computation that PhysX uses.

You could try reducing the mass of one of the objects (whichever is not having forces applied), if this fits with your scenario.

However, I think it may be that the only way to ensure two objects are perfectly 'locked' together, would be to parent one to the other, and remove the rigidbody component of the child - therefore forming a Compound Collider. Only certain types of colliders can do this, however.

(see the section headed "Compound Colliders" on this manual page)

3

Thanks for answer. I've tried to reduce the mass with no luck.

I'm using coumpound colliders for totally fixed bodies. But i don't want to totally fix the configurablejoint. All i want to do is to create a less springy behaviour on locked motion axises. I've tested All-Locked Configurable Joint(ALCJ) vs. spring joint vs. fixed joint. ALCJ feels nearly same as spring joint. But fixed joint looks rock solid.

I think the configurable joint is a base for all other joints and i can produce all other joints by configuring it right. Am i wrong?

5

I was trying to figure this out for quite some time. The only solution I could find to get the effect I wanted was to create reciprocal configurable joints for each object I connected. Meaning if I want to connect objects B and A then B will need a joint with A as it’s connected body and A will need a joint with B as it’s connected body. Then, I set the five Drive and Angular Drive Position Springs on both joints to 9999 or higher while keeping their Position Dampers at 0. The greater the difference between the Position Springs and Dampers the more solid the connection becomes. I would guess it’s an intensive solution but the connection is sweet.

6

If all objects in the chain are more or less similar mass, then it should’ne be springyu (with 0 values in all bounciness etc, and Motion locked, angular limited) , but if one of your objects is way heavier, you will have that wierd effect. So just change mass of all objects to similar.