New Active Property for Joints

We just enabled a new Active property for JointInstances, WeldConstraints, and Constraints.

Active is true when:

  • The joint is Enabled (for Constraints)
  • The joint itself and both of its parts are in Workspace
  • The joint is active in world
    • Always true for simulated joints if the above are true
    • More complicated for rigid joints like Weld, Snap, WeldConstraint, and Motor6D

Welds between two parts in Roblox are mutually exclusive: there can only be one transform between two parts at any one time. When there are redundant welds or welds forming a cycle we might need to ignore some of those welds to prevent potential conflicts.

We have a system called the “spanning tree” that decides which welds are currently being ignored and which are currently active. With the new Active property now you can tell which is which!

This should be useful when we make the change to stop automatically removing redundant welds. Now you know which welds are being ignored and safe to remove!


i wish this property existed for my real life joints



If anyones wondering how he was showing the joint spanning tree around 3:00, its an option under the Physics settings in Roblox Studio, called IsTreeShown:


There are some interesting things to see when its enabled.