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Technical Paper:
Eva Game Rig

When the first X Box was being developed there were several tests being worked on that were designed to show off what it could do. Eva was created to show just how far characters could be pushed in the new engine. The animated test falled way short of what it was hopping to do but the end result did look OK. PEN Productions handled the rigging and skinning of the character rig for Paul Stead that was at Microsoft at the time.

The rig required some dynamic solutions for her breasts and clothing but little was need in the end. The animation on the character ended up being very simple and not pushed as far as it was originaly suggested so the dynamics are not noticable.

Eva was never seen standing up in the final piece, this wasn't known when setting up the character as the story boards were not complete.

In this image you can see the unique FK spine controls that were used.

The control set was limited to just IK arms and legs and and FK spine. This was at the request of the animator that said nothing else was needed.



The shoulder system used stretchy bones that worked on the game engine side. The stretchy bones can be seen inside of the modeled bones. These bones allowed for more realistic defomations for the shoulder area and resolved problems often seen in game rigs.

The brests are driven with a dynamicaly driven bones that can been seen here. As the character moved a Runge-Kutta dynamics solution was calculated to add secondary motion. The motion of the shoulder also pulled on the brest bone so that as the shoulder is raised the chest would be pulled.


The bones were modeled to help fit the volume of the character more closely. This could be turned on and off if needed or the bones could just be hidden.

On the right you can see the bones in the regular state with out the extra modeling on them. A total of XXX bones were used for skinning the character, at the time that this was done this was considdered high.

For the hand the PEN Attribute Holder modifier was used with a custom attribute definition.

The controls were limited as there wasn't to be much hand animation to be done.

Poses can be saved for later use using the PEN Attribute Holder interface. This makes short work of setting up main poses and allows the animator to concentrate on the suttle movements of the hands instead of the broard strokes.

Eva's spine was something that we hadn't tried before. An FK spine was requested by the client but the complaint was FK had to many controls.

Adding just a control at the top and bottom of an FK system and having the mid joints controled with a fixed blend to the top and bottom controls doesn't allow for the sort of flexability that is needed.

The solution was to add a third control that didn't directly bend the spine but instead changed the blend ratio from top to bottom. This allowed the animator to decide where the flexing of the spine would occure.

There wasn't much needed on the feet for this character so the foot rig was kept simple with only the one main on screen control and three slider/spinners to handle foot rolls and toes.