The Motion Dynamics of Snakes and Worms Ryan Kern

Overview Gavin Miller – SIGGRAPH 1988 Mass-Spring system Explicit Euler Integration

Mass-Spring system Series of connected cubes representing segments Each cube is a lattice of springs Mass at each corner Spring along each edge and face-diagonal

Generating Motion Traveling sine wave Directional Friction Varies the “natural” length of axial springs with time and position along body Directional Friction Prevents backwards movement

Motion Types Rectilinear Progression Horizontal Undulatory Progression “inchworm” motion Horizontal Undulatory Progression More familiar snake-like motion Also “sidewinding” and caterpillar motion

Maya Integration MEL script Skeletal / joint-chain data Few nodes (n+1)

Problems Unknown constants! Mass Segment length Amplitude Period/frequency Only interested in lateral movement, so the y-coord is fixed

Potential changes Write a plugin More motions Parameter changes require simulation restart NURBS surface generation using lattice as control points (allows for volume-preservation) More motions With missing data, non-level surfaces are possible (sometimes easy)

Demo I apologize for the head