Metaball Capture
Metaball capture involves capturing points to metaballs rather than bones, which is used when capturing or deforming character geometry. A character’s skin geometry can be captured to a set of metaball groups, just as it can to a set of bones. This is useful because instead of being controlled by the transformations of a relatively small set of bones, metaball capture allows a character’s skin to be deformed by the motion of a large field of metaballs.
Using metaball capture has advantages over capturing to bones. For example, capturing an arm using a single bone for the upper arm and a single bone for the lower arm causes the character’s skin to deform rigidly along with the underlying bones and does not capture more detailed motion in the skin resulting from the motion of underlying muscles. Metaballs provide a more fine-grained approach to capturing and deforming, as each metaball can in theory move independently of every other metaball. Deforming points based on the motion of underlying metaballs makes it easier to model more detailed behavior in a character.
Additionally, metaballs blend naturally together to form a smooth surface, so the when they are used to build the muscular structure of a character, this surface provides a structure over which skin may be inflated so that underlying bulges and movements in a character’s muscles are reflected in the motion of the character’s skin.
Capturing Geometry
Click the Capture Geometry tool on the Character tab of the shelf.
Set the Type parameter to Metaball in the operation controls toolbar.
Select the geometry objects to capture and press Enter to confirm your selection.
Select the metaball objects (for example muscle objects) to capture with and press Enter to confirm your selection.
Note | In order to visualize capture regions on a character’s skin, it is necessary to define a color for each muscle whose capture region you wish to visualize. This can be done by turning on the Add Custom Color toggle on the Preferences tab of the muscle object. |
This procedure creates two new nodes in the network of the captured skin geometry: a 
Capture Metaball surface node and a 
Deform Muscle surface node.
The Capture Metaball surface node associates capture regions with each muscle specified during the capture and assigns a capture weight for each region to each point in its input geometry.
The Deform Muscle surface node actually deforms the skin geometry according to the motion of the underlying metaballs. It also provides more advanced features such as inflation of skin over underlying muscles.