Kim Sauvé, Lancaster University
Dominic Potts, Lancaster University
Jason Alexander, (then) Lancaster University
Steven Houben, (then) Lancaster University
As physicalizations encode data in their physical 3D form, the orientation in which the user is viewing the physicalization may impact the way the information is perceived. However, this relation between user orientation and perception of physical properties is not well understood or studied. To investigate this relation, we conducted an experimental study with 20 participants who viewed 6 exemplars of physicalizations from 4 different perspectives. Our findings show that perception is directly influenced by user orientation as it affects (i) the number and type of clusters, (ii) anomalies and (iii) extreme values identified within a physicalization. Our results highlight the complexity and variability of the relation between user orientation and perception of physicalizations.
The design of the 6 exemplar physicalizations is informed by the well-known static physical bar charts often used in physicalization. Each of the physicalizations consists of 16 blue acrylic objects that vary in 4 lengths. This allowed us to create a range of complexity, while keeping them similar in density:
The layouts of the 6 physicalizations were created by applying different visual properties informed by what is known in 2D visualization as pre-attentive visual properties:
Proximity was used to create differences in internal and external distances between objects. Additionally, we created two different types of spatial relations: either in a grid or linear fashion.
Continuity was used to create differences in perceived connectedness, either by using objects of similar size or objects of increasing size in a consecutive manner.
Atomic orientation was used to create differences in the orientation of the individual objects within the physicalization, either in the x, y or z plane.
We presented each of the 6 exemplar physicalizations from four orientations - North, East, South and West - to cover the major viewing angles. We propose orientation consistency as new terminology for a measure of the consistency of user responses to information retrieval tasks across different orientations.
A total of 20 participants participated in our study. They were consecutively presented with 24 different physicalizations, the 6 physicalizations each seen from the 4 orientations. For each of the 24 physicalizations, we asked the participants to complete 3 different information retrieval tasks:
Can you identify any groups of objects?
What is the group that stood out first to you?
Can you point out the highest and lowest value(s)?
Our results show that user perception is directly affected by orientation, resulting in a systematic lack of consistency across tasks, participants, and physicalizations. We found that occlusion is one of the primary reasons for these inconsistencies, and can be divided into 3 types:
Continuity occlusion occurs when a set of objects seems to be intersected, which prevents someone to see the full continuity.
In this orientation of phys3, a cluster of 3 cubes was identified, as one of the cubes is occluded by the larger cluster on the left.
In this orientation of phys3, the continuity of the cubes is not occluded, leading to a cluster of 4.
Proximity occlusion occurs when the perceived distance between objects appears either further or closer together, which prevents someone from seeing the true proximity.
In this orientation of phys5, the objects were perceived as 3 clusters.
In this orientation of phys5, the front cluster occludes the objects in the back, which makes the distance between them appear shorter, and therefore they were perceived as one.
Atomic orientation occlusion occurs when objects of different forms are perceived similar or when objects of similar form are perceived different, due to their atomic orientation.
In this orientation of phys4, the objects were clustered by size.
In this orientation of phys4, objects of different size were perceived similar due to the perspective of the viewer, leading to one large cluster.