Energy Brushes: Illustrating Elemental Dynamics (UIST 2016)

Dynamic effects such as waves, splashes, fire, smoke, and explosions are an integral part of stylized animations. However, such dynamics are challenging to produce, as manually sketching key-frames requires significant effort and artistic expertise while physical simulation tools lack sufficient expressiveness and user control.

Couple of years back, I came across Joseph Gilland’s “Elemental Magic” at the siggraph book store. As I was flipping through the pages, I was fascinated by the techniques and process of hand-drawn special effects animation. A classical hand-drawn approach to design these animation effects is to use energy strokes for implicit guidance. Artists design special effects by sketching the gestures that coarsely define the underlying forces (e.g., heat ascension, air expansion, water drift). This approach enables artists to focus on the core underlying forces, exaggerate, stylize, and compose intriguing dynamics by the interaction of these forces, while preserving the fluidity of sketching.

Inspired by this, we present an interactive interface for designing these elemental dynamics for animated illustrations. Users draw with coarse-scale energy brushes which serve as control gestures to drive detailed flow particles which represent local velocity fields. These fields can convey both realistic and artistic effects based on user specification. This painting metaphor for creating elemental dynamics simplifies the process, providing artistic control, and preserves the fluidity of sketching. Our system is fast, stable, and intuitive. An initial user evaluation shows that even novice users with no prior animation experience can create intriguing dynamics using our system. Kudos to Jun Xing for pulling this altogether. Read the full paper below.