Children of a hingejoint not colliding with parent's mesh when connectedBody is assigned

Questions & Answers
1

Imported an FBX mesh of a rover (something like a primitive Mars rover), with a robotic arm.

I’m working on the first HingeJoint, got it working to satisfaction operating the first section of the arm.

If I use the connectedBody property to connect the hinge to the bot’s “parent” Rigidbody, the arm does not collide with the mesh of the bot (it passes right through it).

When I remove the connectedBody, it collides as expected (and operates while the bot is not moved), but of course when the bot moves, the arm basically falls off (and behaves oddly).

Mye objective is to enable the collision of the arm’s mesh with the bot’s mesh, but it seems that such collisions are disabled between the children of the hinge and the connected body.

I was considering manual configuration of the connectedAnchor, but I’m not exactly sure how to go about it.

Should I write script in the parent to the hinge so that fixed update positions the hinge’s anchor or connected anchor?

Is there a way to re-enable “self collision” of this bot?

Many thanks.

2

Yes, by default the collision between connected bodies are disabled because when their colliders overlap they would get seperation forces applied. However if you ensure proper setup so the two connected bodies can rotated without overlap except at extremes you can simply enable collisions with the enableCollision property. You can simply enable them in the inspector as well.

Note that using limits for each hinge joint usually gives better results