Tracking the orientation of a sphere

[abecker5]

We're tracking the orientation of a large inflatable ball about 2 feet in diameter. We'd like to accurately record the orientation of the ball as it rolls around the workspace.

• Should we use one trackable, or several?
• As the ball rolls on the floor, many markers will be obscured -- will this cause problems?
• Is 'more markers' better than 'few markers'?
• How can we easily set the pivot point to the sphere center?

If anyone has encountered/solved this problem, we'd appreciate tips. We'll post solutions as/if we find them.
Thanks

[NaturalPoint - Mike]

Hello -

When creating rigid bodies, you can design them to be tolerant to marker loss to a point. More is better, however due to the exponential increase in difficulty of solve with each additional marker, you should not go over 7 markers in a single rigid body.

What I would probably do is create two distinct marker arrangements at the poles of the sphere. You can then use the position and orientation of those two rigid bodies combined with accurate measurements of the sphere itself to get the precise position and orientation.