Skeletons

Making a skeleton in Autodesk Maya is fairly simple but you will need to decide what kind of animation it needs to result in to use the proper commands along the way.

Skeleton creation

A basic skeleton can be made using the Joint Tool (the red arrow) from the "Animation" tab in the default tab shelf.

Here are the basics of joints and the joint tool in Maya.

  • With the joint tool selected simply left click to make a new joint. Successive clicks will continue the joint chain and add a joint as a child of the previously made joint.
  • Two chains of joints can be joined by simply parenting one to another. Select the child (the start of one chain), select the parent (the end of another chain), and then use the "Parent" command from the "General" tab shelf. You can also just press the "P" key once both are selected.
  • You can start a new "branch" of a skeleton by simply clicking on a joint while the Joint tool is selected and then clicking the desired position for the new joint.
  • You CAN just use the translation tool to move joints around but it will move the children of that joint accordingly.
  • Since a joint is nothing but its axis you can use "Pivot mode" to move a joint without moving the children of that joint. Either toggle it by pressing "Insert" or activate it temporarily by holding the "D" key and you can move a single joint by itself even if it's in a chain of joints.
  • You can hold down "Shift" while clicking to make new joints to lock the new joint into intervals 45 degree from the previous joint.
  • You can mirror a joint, or chain of joints, by clicking the "Mirror Joint" button (the blue arrow) within the animation tab shelf. To change the direction of the mirroring Double-Left-Click the icon and select the appropriate mirror direction from the window that pops up before selecting "apply".

    You only need to have the root bone of a chain selected to mirror it. The new copy should automatically be made a child of the same parent the original had.

    You can only mirror one chain at a time.
  • If the scale of the visible joints are too small or too large for your particular model you can Double-Left-Click the joint tool and look for "Short Bone Radius" under the "Bone Radius Settings".

Skeleton Binding

Once a skeleton is in place you can bind it to a mesh fairly easily.

  1. Select the root bone in the skeleton that are to be bound to the mesh (No, you do not need to select all of the bones).
  2. Select the mesh object.
  3. If it is not set already use the layout dropdown to change the interface mode to "Animation".
  4. With both the root bone and mesh selected you can select a bind command from the main menu. For instance to apply a Smooth Bind select "Skin > Smooth Bind".

You can also use the "Interactive Bind" command to bring up weighting indicators that allow you to adjust the default weighting envelopes of the skeleton. I don't recommend doing this as the vast majority of meshes you'll work with will require fine tuning via Skeletal weighting with the "Weight Tool" anyway.

Skeletal weighting

The primary way to assign weighting to joints within Maya is via the "Paint Weight" tool. Even if you want to change the weight values of individual vertices then you'll go through this tool interface.

The "Paint Weight" tool is identified below.

For the Paint weight tool to work you need to also have the mesh you wish to work with selected at all times. Make sure not to confuse selecting joints within Maya's Outliner list of objects in the scene and the Tool Settings own list of joints.

Otherwise you can follow these steps for a basic weighting process.

  1. Select the mesh whose weights you want to edit.
  2. Select the Paint Weight tool within the "Animation" tab shelf. If the "Tool Settings" pane is not already open then Double-Click the "Paint Weight" tool icon to make it appear with the Paint Weight tool settings.
  3. Under the "influence" drop down of the Tools Settings pane you should see all joints that have been assigned to the currently selected mesh. Select the joint whose weighting you want to modify.
  4. While you still have the Paint Weight tool selected you'll see the mouse cursor change to a paint brush.
    • While in this mode you can "paint" weighting directly onto the mesh. Left-Click/ to add weighting to part of a mesh and hold down "Alt" while Left-Clicking to remove weighting from part of the mesh.
    • While in this mode the surface color of the mesh should change. White areas denote more weighting while black areas denote less weighting.

When painting, if the radius of the brush is too small or too large, look under the "Stroke" section of the Paint Weight tool settings to change the radius of the brush area.

Also keep in mind you may need to change your viewport settings to see the weighting effects (you can't be in wireframe mode for instance).

Manual selection

If you wish to assign particular weight values to exact vertices then you can simply change the "Mode" radio dial from "Paint" to "Select". These options are found directly under the Influences list within the Tool Settings while you still have the Weight Tool selected..

Also know that if you want to manually assign weight values you may wish to change the "Normalize Weights" mode from the default of "Post" to "Interactive". Who decided on these names???? This will allow you to adjust the "Value" slider and have the weighting of other joints attached to the selected vertices changed automatically as you adjust the weighting.

One problem of trying to select vertices manually in Maya is that it has a habit of selecting bones within the model when you want to select the vertices. You may need to turn off bones from being displayed to get around this.

Moving joints after binding

If you absolutely, positively have to move a joint after it has been bound weighted then you'll need to detach the skin temporarily. Follow the steps below to retain the weighting you've applied to the model.

  1. Select the skin / mesh of the model.
  2. Select "Skin > Detach Skin" but make sure to select the expanded options by clicking the square next to the entry in the menu.
  3. In the new window change the "History" option to "Keep history".
  4. Press "Detach" in the same window.
  5. The bones are now detached from the model. Adjust the joints as needed (be mindful of any symmetry you may have applied).
  6. Once you are happy with the new joint positions use the "Smooth Bind" command just as you did to bind the joints the first time. The skin / mesh should remember the weighting used by each bone.

Of course this works best when you are simply adjusting the bone positions. Adding or deleting bones will of course interfere with the previous weighting and may require re-weighting parts of the model.

There are actually several different methods to how a skin can be bound to a skeleton in Maya. These can be found within the extended Smooth binding options under the skin menu.

You can find a break down of the differences in this video by Steven Roselle...

https://www.youtube.com/watch?v=ZyytEiB-1Ug