Section: New Results

Interaction with spatial augmented reality for physical drawing

Participants : Jérémy Laviole, Martin Hachet.

We developed tools that enable precise interactive projection on pieces of paper. The sheets of paper are tracked by a camera while the user's inputs (e.g., touch and hovering events) are detected by a Kinect. The paper acts as a screen, its image coming from an overhead projector. The focus of this work is to use such tools to assist the creation of physical drawings and painting. In this context we propose Digital Construction Lines (DCL), in opposition with physical construction lines. Traditionally, the structure of a physical drawing can be created with construction lines which are light pencil strokes. These strokes are then erased during the drawing process. With DCL, it is not required to erase the construction lines anymore. Furthermore, it is possible to create construction lines on fragile material like a canvas for waterpainting or on fresh paint. It also enables construction lines on a dark canvas. In addition to these projection advantages, it is possible to create these DCL interactively and directly onto the support. Consequently, the DCL complement the physical ones during the creation process.

Figure 4. Using Digital Construction Lines for spatial augmented reality-based physical drawing.

We investigated in a user study if the DCL could effectively replace the physical construction lines, and compared the performance (speed, cleanliness) between the two kinds of construction lines. In this user study we also evaluated the quality and usability of projection of thin lines in a fully controlled environment with a low-cost setup. The study showed that DCL could effectively replace physical construction lines, even though it might not be desirable. The study also showed that the drawing experience was as pleasant with projection, and with the usual tools. The feedback about the quality of tracking and projection was also positive. The only negative evaluation concerned the size of the projection area, which was limited by the resolution of the projector. This work was published as part of Jérémy Laviole's PhD thesis [4] .

PapARt was also used as part of a museum exhibition on the Lascaux caves, together with other 3D UI from Potioc. This exhibitation has provided us with the opportunity to experiment with touch-based interfaces for manipulating 3D virtual objects. We targeted three tasks: observing rare objects with Cubtile, reassembling object fragments with Toucheo, and reproducing artwork with PapARt [7] (see Figure 5 ). These exhibitions allowed us to experiment our systems in real conditions. It led to a Living Lab, where the visitors can test our devices.

Figure 5. Manipulation of a 3D model and lighthing conditions for drawing on a prehistoric object in a museum.