Sketcholution: Interaction histories for sketching

• We present a history mechanism for sketching that captures drawing on a stroke level.
• We propose two history visualizations for sketches based on stroke clustering.
• One technique is a comic strip that shows sketch evolution over several frames.
• Another is a summary frame that numbers the changes in a single image.
• A user study found significant improvement for sketch summaries over animation.

We present Sketcholution, a method for automatically creating visual histories of hand-drawn sketches. Such visual histories are useful for a designer to reflect on a sketch, communicate ideas to others, and fork from or revert to an earlier point in the creative process. Our approach uses a bottom-up agglomerative clustering mechanism that groups adjacent frames based on their perceptual similarity while maintaining the causality of how a sketch was constructed. The resulting aggregation dendrogram can be cut at any level depending on available display space, and can be used to create a visual history consisting of either a comic strip of highlights or a single annotated summary frame. We conducted a user study comparing the speed and accuracy of participants recovering causality in a sketch history using comic strips, summary frames, and simple animations. Although animations with interaction may seem better than static graphics, our results show that both comic strip and summary frame significantly outperform animation.