Authoring motion cycles

Motion cycles play an important role in animation production and game development. However, creating motion cycles relies on general-purpose animation packages with complex interfaces that require expert training. Our work explores the specific challenges of motion cycle authoring and provides a system simple enough for novice animators while maintaining the flexibility of control demanded by experts. Due to their cyclic nature, we show that performance animation provides a natural interface for motion cycle specification. Our system allows the user to act several loops of motion using a variety of capture devices and automatically extracts a looping cycle from this potentially noisy input. Motion cycles for different character components can be authored in a layered fashion, or our method supports cycle extraction from higher-dimensional data for capture devices that deliver many degrees of freedom. After capture, a custom curve representation and manipulation tool allows the user to coordinate and control spatial and temporal transformations from a single viewport. Ground and other planar contacts are specified with a single sketched line that adjusts a curve's position and timing to establish non-slipping contact. We evaluate the effectiveness of our work through tests with both novice and expert users and show a variety of animated motion cycles created with our system.