Center of Mass (Rig)
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The Center of Mass is a unique point that characterizes movement of an object (or a group of objects) as a whole. When a linear force is applied to the center of mass, it causes linear acceleration without angular acceleration.
A Center of Mass is required for Physic Tools to work properly.
More about this here.
Creating Centers of Mass
To create a center of mass:
1. Switch to the Rig mode:
2. Select one or several Rigid Bodies.
3. Go to the Rigging Tools panel.
4. Open the Main actions panel:
5. In the Prototype center of mass section, click Add:
Keep in mind that creating a new Center of Mass causes a couple of issues.
First, Direction Controllers won’t work properly.
This can be fixed by connecting them to the Center of Mass:
1. Switch to the Rigging Mode.
2. Select Direction Controllers.
3. Select the Center of Mass.
4. Connect them by selecting CenterOfMass → Connect with dir controllers from the Commands menu:
Second, Ballistic Ghosts won’t render with a newly created Center of Mass. To fix this, you’ll need to snap the mesh to it:
1. Switch to the Mesh Mode.
2. Select every mesh that makes up your character.
3. Switch to the Point Controller Mode.
4. Select the Center of Mass.
5. Use Commands → CenterOfMass → Snap mesh to the center of mass:
After you take care of these two issues, everything should work as intended.
Multiple Centers of Mass
A character might have more than one Center of Mass.
Here, we have a center of mass for the character and another one for the sword the character is holding.
In cases you have two or more CoMs, you might want to add a composite Center of Mass for the entire character.
For example, if you have two characters interacting, a composite center of mass can be used to monitor the characteristics of their interaction.
To create a composite Center of Mass:
1. Switch to the Rigging Mode.
2. Select every Center of Mass.
3. Use Commands → CenterOfMass → Create composite:
The composite Center of Mass, like a regular one, should be connected to the meshes and Direction Controllers, as described above.