Skinning a character to a skeleton

This is a quick and dirty guide to skinning for this assignment. It shows the steps for skinning the Woody model onto a skeleton with mocap data for the walking sequence. See the Maya tutorials for further and more detailed information on character setup.

1. Load the skeleton/mocap data

Open the script editor (Window | General Editors | Script Editor) and load the bvhimport.mel script. Run the script (Ctrl+Enter) and open the file Walking.bvh. Once it has finished importing the sequence, return to the main window and zoom the view out until you see the skeleton. (The scale of the mocap data is large compared with the default view in Maya.) Adjust the Playback End Time to 110 (which is the last frame of this particular clip). Play the animation to see the skeleton walk. Set the current time back to -20.00 which puts the skeleton in a T-pose.

2. Load the skin/model

We now want to import a model (as opposed to "open"). Goto File | Import and select woody.mb. This loads the woody model. Notice that there is already a skeleton inside this model. We want to delete this skeleton. Select it by rubber-banding around it and press the Delete key.

3. Alignment and binding

Next we need to align the skeleton with the model. In our case, you can actually get away with either moving the skeleton to the model or moving the model to the skeleton. (This is because there is only one translation parameter (connected to the hip) in .bvh files. The rest are rotations relative to the parent nodes.) You will probably want to use the top/side/front orthographic views (under Panels) to help you align it perfectly.

Note that we get lucky here that the woody character has the same dimensions as the mocap skeleton. In general, the character model may have different scales, limb sizes, and even number of joints. Thus, you will have to scale the initial skeleton (e.g. in the t-pose) to fit the model.

Once they are aligned, use the Outliner to select both the the woody model and the skeleton. (Note that we don't want to select the bvh_import object but rather the skeleton hierarchy nested within it.) Then bind them together (Skin | Bind Skin | Rigid Bind). (Note that you could also do a smooth bind. The Maya tutorial has more information of the differences between a rigid and smooth bind.)

Now when you playback the animation, the model will be skinned onto the skeleton.