Agile 3D Sketching with Air Scaffolding

Hand motion and pen drawing can be intuitive and expressive inputs for professional digital 3D authoring. However, their inherent limitations have hampered wider adoption. 3D sketching using hand motion is rapid but rough, and 3D sketching using pen drawing is delicate but tedious. Our new 3D sketching workflow combines these two in a complementary manner. The user makes quick hand motions in the air to generate approximate 3D shapes, and uses them as scaffolds on which to add details via pen-based 3D sketching on a tablet device. Our air scaffolding technique and corresponding algorithm extract only the intended shapes from unconstrained hand motions. Then, the user sketches 3D ideas by defining sketching planes on these scaffolds while appending new scaffolds, as needed. A user study shows that our progressive and iterative workflow enables more agile 3D sketching compared to ones using either hand motion or pen drawing alone.