PhysInk: Sketching and Understanding Behavior

Project Lead: Jeremy Scott

Despite the prevalence of CAD software (e.g. SolidWorks or Rhino), there is no easy way to describe physical behavior to a computer. For example, during the ideation stage of product design, designers use pen-and-paper or whiteboards to brainstorm about physical mechanisms. Unfortunately, these static sketches are not ideal for conveying motion, requiring the designer to both draw arrows representing movement and redraw the device in multiple storyboard frames. To address this gap, we have built a sketching application called PhysInk that allows users to naturally describe physical behavior.

Users sketch a device's parts and constraints (joints) on a canvas containing a 2D physics engine. The resulting sketch is interactive, enabling the user to move the parts directly on the canvas, subject to their constraints. This is intended to produce an experience similar to manipulating the physical device, providing a natural way for the user to demonstrate their vision of the device's behavior.

In response to the demonstration, PhysInk builds an understanding of the behavior using a timeline knowledge representation, consisting of physical events, event geometry and causality. The system uses the timeline to reason about the equivalence of multiple behaviors. It can also be used to produce a physically-realistic version of the user's description. PhysInk's user interface and timeline knowledge representation make it one of the first tools to allow the user to directly describe behavior, rather than structure that leads to that behavior.

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