An Ephemeral Approach to 3D Character Rigging

What is it?

The Ephemeral Rig is a plugin I created for Autodesk Maya.

It was created for my Masters of Computer Science at Kutztown University and written in C++ using the Maya C++ API.

The plugin is accompanied by a research paper explaining my methodologies and findings.

Demo Video

The plugin represents a new solution to a problem in rigging - how to blend between two separate modes of animation - Forward Kinematics and Inverse Kinematics.

Traditionally, the animator blends between the two modes. This transition can cause unexpected behavior.

In the ephemeral rig, each joint is disconnected from all the other joints in the scene at rest. When the animator interacts with a joint, a background node graph builds the connections on the fly to act as either Forward or Inverse kinematics.

This removes the need for the blend, as the rig is in either forward or inverse mode exactly when needed.

What does it do?

This image illustrates how an arm rig works with the ephemeral system.

At rest, there are no connections between the joints themselves. Each joint has a corresponding node that has connections to the other ephemeral nodes.

In forward mode, when the animator moves the shoulder joint, the connections of the shoulder ephemeral node are checked.

Since connections are found, the joints are connected in the same manner as the nodes, and the rig is now in Forward mode.

When the animator is finished, the joint connections are destroyed and the scene returns to a neutral state.

The inverse mode works in the same way, except when the wrist is moved the connections flow back up the arm.

Abstract

All 3D animated characters share one thing in common: a rig. The rig is what controls a character’s movements. Nearly all rigs are manipulated through two basic methods: forward and inverse kinematics. The two kinematics need to blend together to achieve the full range of behavior desired by the animator. For the past 20 years, this blend has been achieved by swapping the character’s rig between two separate kinematic rigs. This blending is clunky, unintuitive, and prone to mismatches and instability.

This thesis focuses on a new approach to rigging with a design called ephemeral rigging. Instead of two separate rigs preset in either forward or inverse kinematics and constantly swapped between, each joint in the character’s rig is treated as a node with possible incoming and outgoing connections. When the animator interacts with a joint, the connections are created at that moment in the specified kinematics mode chosen by the animator. This allows one rig to act as both forward and inverse, reducing complexity and increasing ease of use.