Skeleton is a special purpose deformation object typically used for controlling bodies in character animations. When the skeleton is modified, the attached objects are modified accordingly.

To create a skeleton representing a leg:

1. Activate the Skeleton tool from the 'Construction' tool tab.

2. Take a side view. Click the first point at the hip bone. Now, move the mouse towards the knee but don't fix the position for the knee yet. We will have to define proper constraints for the thighbone first. Rotate the mouse upwards so that it represents the knee in its uppermost position. Then move the mouse to the opposite direction so that it shows the position of the knee in its back position. Then move the mouse to a position between the two extreme angles and to a suitable distance (the length of a thighbone) and fix the second point (the knee) by clicking the mouse.

3. Then move the mouse towards the ankle and repeat the steps above in order to define constraints for the shinbone as well.

4. Next define a bone from the ankle to the tip of the toes (we do not create toe bones this time) with appropriate constraints. Then select 'Accept' from the pop-up menu to terminate the skeleton creation.

Then you can bind the skeleton to a target object (such as a SDS mesh representing a human body) using appropriate binding tools.

Skeletons can also be grouped to hierarchical structures to represent, for example, the bone structure of a human body.

To create a hierarchical skeleton, say a spine with two legs:

1. Switch to the side view and create a skeleton representing the spine of a human body.

2. Create a skeleton representing a leg.

3. Drag & drop the leg inside the spine. The leg is now a sub object of the spine.

A hierarchical skeleton system

4. Repeat the steps 3 and 4 to create another leg. Then select the legs and click the 'Attach' tool. This attaches the legs to the spine so that if you drag one of the leg joints far enough, the effect will propagate to all three skeletons.