SandCanvas: A Multi-touch Art Medium Inspired by Sand Animation
SAND ANIMATION ANALYSIS
To better understand the special requirements of our new medium we sought to enumerate the gestures commonly used by sand animators. After a meticulous observation of
30 sand animation videos, we identified a set of sand animation techniques commonly employed by artists.
Common Sand Animation Techniques
Sand animation has pouring and manipulation techniques.
Pouring is an additive technique that varies depending on how much of the canvas is affected. Canvas pouring is used to set the texture and initial context for painting (Fig. 2 left), or, to change context while storytelling. Skinny pouring is used to draw tiny details, lines, and shapes (Fig. 2 right).
Sand manipulation techniques move sand rather than adding it. We classified these techniques by how the artist’s hand interacts with sand. Fingertip drawing traces out lines with the tip of one or more fingers (see Figure 3 left). While, finger carving (see Figure 3 right) uses the whole finger, typically the index finger, small finger, or the outside of the thumb, for drawing and fine tuning shapes.
Artists do not use their fingers exclusively. Palms are often used to create semi-elliptical, or spiral like patterns, such as clouds. We call this technique palm rubbing (see Figure 4 left). Whole hands are often used to make big sweeps to clear the canvas and set up a new context for the animation, which we termed hand sweeping (see Figure 4 right).
One final technique that bears mentioning is actually a special version of other techniques. Sand animators will sometimes use both hands simultaneously to quickly draw or pour symmetrical patterns in sand (see Figure 5). This technique, which is quite rare in other artistic media, is very common in sand animation.
These techniques can be combined to fluidly transform one image into another (see Figure 6), creating surprise and conjuring emotion. Here lies the beauty of sand animation.
Taxonomy of Sand Animation Gestures
After listing common sand animation techniques, we saw many similarities and differences between them. To better compare and contrast these techniques, we created the low- level taxonomy of gestures found in Table 2. While there are other gesture taxonomies in the literature [10, 33], we needed one that was created specifically for multi-touch art work like sand animation.
Canvas Fingertip draw
Skinny Finger carve
Symmetrical Hand Sweep
Table 1: Common sand animation pouring and manipulation techniques. Symmetrical is a modifier that can apply to both pours and manipulations.
We manually classified gestures along five dimensions: mode, form, precision, hands and actuation. Mode separates pouring gestures from manipulation gestures. Form indicates any motion in the gesture. In static gestures, the hand is held in one position and one configuration, while dynamic gestures change the position or configuration of the hand. (This is similar to the pose and path concepts in Wobbrock et al.’s gesture taxonomy ) The precision of the gesture can be coarse or fine, and the hands dimension indicates the number of hands involved in a gesture: one (uni-manual) or two (bi-manual).
Figure 2: Canvas pouring (left) creates background textures, while skinny pouring (right) is for drawing lines.
Figure 3: Fingertip drawing (left) and finger carving (right) to create and manipulate shapes.
Figure 4: A palm rub (left) draws cloudy patterns, and a hand sweep (right) clears part of canvas.
Figure 5: Symmetrical hand sweep (left) & skinny pour (right).
Figure 6: Fluid transformation of images.