Applying Reach in Direct Manipulation User

Interfaces

Aaron Toney, Bruce H. ThomasSchool of Computer & Information Science

University of South Australia

Common Sense and Math

• If you can not convert your “common sense” into a quantifiably testable hypothesis then at best you don’t understand what you are talking about.

• In order to be useful for use for human authored code design rules, principals, and practices need to be expressible in qualitative terms.

• The paper uses set notation to encode and test what are otherwise “common sense” relationships. This formal notation was used as it allows programmers not only gain intuition about their users environment but immediate insight into how to implement the software algorithms behind applications dynamically based on user reach.

What we show in the paper

• For individuals, depth of reach predicts the segmentation of the working plane into working and storage areas.

• For collaborating users regions of overlapping reach enable prediction the formation, size, and shape of shared group spaces.

• Applied models of reach predicts the rough impact of such variables as working surface size, height, shape, and number of users on the working surface’s utilization.

The Reach Envelope

• Direct manipulation user interfaces are constrained to areas reachable by the user.

• The On Table Reach Envelope (OTRE) represents the boundary of the set of all reachable points (SR) .

An Individuals Reachable Space

• Reachable space (SR) is the total space reachable by either hand (AL U AR)

• Bimanual reach (SRB) is (AL ∩ AR)

• For individuals working space (SW) is equivalent to SRB and the storage space (SS) is the relative complement of the total reachable space and the working space (SR - SRB).

A Groups Reachable Space

Under the hypothesize that group spaces are formed in preference to personal spaces group space:

• Group space (SRG) can be described as the intersection of all users’ reachable spaces (∩SR)

• Co-located working space (SW) can then be described as the reachable area that is not a group space (SRB - ∩SR ) or (SRB - SG). These definitions agree with both the observations in the literature and the results of the user study presented in this paper.

Converting “Common-Sense” about Reach into testable Hypothesis

• Working space (SW) is primarily contained within the most easily reachable areas.

• Highest usage will occur in the area of bimanual reach (SRB), while lowest usage will occur in areas reachable only by one hand (SR -SRB).

• In general group spaces will form in preference to personal spaces.

• For each user and task there is an ideal working distance (RIDEAL), where reach working surface usage probability is attenuated for distances other than RIDEAL.

What do Simulations Tell us about user Reach?

(All simulated subjects are anthropometrically representative of

the 50% females seated 17.5 cm from the working surface)

Simulated reach at 80, 90, and 100cm square tables.

Workspace utilization is sensitively dependent on table size : An Increase in table size of only 10cm on a side is predicted to loose the comfortable communal reach region

Predicted on table reach probability for adjacently seated users

(90 and 120 centimetre tables shown)

Impact of Inter Subject Angle

Decrease in inter subject angle causes:• Overall decrease in both private and working

spaces• Increase in available group space on the table

(45 and 90 degree tables shown)

What we learned from initial user studies

(Sixteen subjects performing a LEGO sort and assembly task. Subjects given 997 LEGO pieces mixed in with 150 model pieces. There was a45 minute time limit and Hand position tracked with Polhemus sensor. Results presented in thresholded spatial histogram.)

Study Observations

• In general results confirmed the authors working hypothesis:– Working space (SW) can be seen as

the reachable area that is not a group space (SRB - ∩SR ) or (SRB - SG).

– Highest usage will observed in the area of bimanual reach (SRB)

– Lowest usage occurred in areas reachable only by one hand (SR -SRB).

– Group spaces tended to formed in preference to personal spaces.

• Regions of overlapping reach were shown to help explain territoriality and the size and shape of collaborative areas observed in Scotts (2003, 2005) example from that work shown right.

Applying Reach

Questions?