The Joint panel is slightly different between setup and animation modes.

Setup

The New button creates a new, unconnected joint.

The Connect button can be used to connect two joints with a bone. To connect two joints, select the first joint, click Connect, then select the second joint. It is often useful to connect various joints together with extra bones to give your skeleton a rigid structure.

The Nailed button displays and controls whether the selected joint is nailed. Remember that nailed joints are not moved by IK, so nail a joint when you want to fix it's position. The Nail setting is keyframed, so nailing can be controlled during animation. Also, it is sometimes useful to nail joints temporarily for easier posing. Note: you can also nail joints using the Nail column in the bone list.

Flex(ion) is similar to nailing. The lower the flex for a bone, the less likely it will move due to IK. A bone is nailed when it's flex becomes zero.

Animate

The Flex and Nailed controls are the same as in setup mode.

The Sharp button controls the type of keyframes recorded for this joint. When Sharp is enabled, keyframes for the joints will be recorded with sharp splines instead of smooth splines.

Normally, trueSpace connects all keyframes with a smooth spline. Most of the time, this smoothing is useful and adds naturalism to movements. Frequently, however, you will want a joint to move directly between it's keyframes with no smoothing. Example: when a character plants a foot, spline smoothing will add a unwanted sliding motion to the foot. By setting the joints in the foot to Sharp and recording the keyframes, the slide can be eliminated.

It is suggested that Sharp mode be used whenever a joint is recorded as Nailed.

Floor provides a simple type of joint constraint. When floor is enabled for a joint, the current z position of the joint is stored as the floor limit. Joints with the floor constraint will never drop below the floor z.