Space-time sketching of character animation

摘要

We present a space-time abstraction for the sketch-based design ofrncharacter animation. It allows animators to draft a full coordinatedrnmotion using a single stroke called the space-time curve (STC).rnFrom the STC we compute a dynamic line of action (DLOA) thatrndrives the motion of a 3D character through projective constraints.rnOur dynamic models for the line’s motion are entirely geometric,rnrequire no pre-existing data, and allow full artistic control. The resultingrnDLOA can be refined by over-sketching strokes along thernspace-time curve, or by composing another DLOA on top leadingrnto control over complex motions with few strokes. Additionally,rnthe resulting dynamic line of action can be applied to arbitraryrnbody parts or characters. To match a 3D character to the 2Drnline over time, we introduce a robust matching algorithm based onrnclosed-form solutions, yielding a tight match while allowing squashrnand stretch of the character’s skeleton. Our experiments show thatrnspace-time sketching has the potential of bringing animation designrnwithin the reach of beginners while saving time for skilled artists.