Seongkook Heo, Yong-ki Lee, Jiho Yeom and Geehyuk Lee


Object snapping found in many layout applications helps users to align objects precisely to snapping references such as the center of a canvas, the center of a reference object, or object edges. When snapping another object to such references, there are several choices regarding which part of an object should be used for alignment. Shown in Figure 1 this may be the edge or the center of a bounding box. While aligning an object using its bounding box edges proves intuitive to fit the end of an object to the snapping reference, aligning an object using its center may confuse due to different ways to determine a center of an object. Since the snapping functionality has an inaccessible area around its snapping reference, it can interfere with the user rather than being of help if there is a discrepancy between the perceived center and the center defined by a system. The bounding box center is the most commonly used point for snapping an object with its center. However, a bounding box center does not reflect the geometry of an object, as we perceive centers of objects differently in relation to their shape and even if bounding boxes of different shapes are the same.

Resulting from previous research on human visual perception and the role of the centroid, we assumed using the centroid, rather than the bounding box center, would provide a better way to help users with aligning objects. Thus, through a user study, we examined the position of a center perceived by a user when aligning objects. Further, we analyzed position differences depending on the object’s shape. Finally, we discussed whether the current snapping algorithm can support such differences, and suggested a new adaptive snapping algorithm based on our findings.


  • Seongkook Heo, Yong-ki Lee, Jiho Yeom, Geehyuk Lee, 2012.
    Design of a Shape Dependent Snapping Algorithm,
    In Proceedings of the 2012 annual conference extended abstracts on Human factors in computing systems (CHI EA ’12), ACM, Austin, TX, USA


User-selected centers