Assessing Lag Perception in Electronic Sketching Ugo Braga Sangiorgi Vivian G. Motti François Beuvens Jean Vanderdonckt Louvain Interaction Laboratory, Université catholique de Louvain - Belgium
Electronic sketching has received a recurrence of interest over the years and again nowadays within the mobile web context, where there are diverse devices, operating systems and browsers to be considered. Multi-platform (e.g. web-based) sketching systems can be constructed to allow users to sketch on their device of preference. However, web applications do not always perform equally on all devices, and this is a critical issue, especially for applications that require instant visual feedback such as sketch-based systems. This paper describes a user study conducted to identify the most appropriate response rates (expressed in frames per second) for end users while sketching. The results are expected to guide stakeholders in defining response parameters for sketching applications on the web by showing intervals that are accepted, tolerated, and rejected by end users.
Citation preview
1. Assessing Lag Perception inElectronic SketchingUgo Braga
SangiorgiVivian G. Motti Franois BeuvensJean VanderdoncktLouvain
Interaction Laboratory,Universit catholique de Louvain -
Belgium
2. Agenda The lag problem Sketching on many devices Experiment
Results Conclusion2 3. What makes a device un/suitable for
sketching? 3 4. Lag4 5. Lag in electronic sketching 133 points 60
Hz 60 FPSper second75 Hz 75 FPS 5 6. Refresh rate Example:
http://frames-per-second.appspot.com/ 30 FPSo (1000/30) = 33
miliseconds 6 7. Sketching on many devices HTML5 7 8. Sketching on
many devices HTML5 1.4 devices per person by 2016 11 - CISCOs
Visual Networking
Indexhttp://www.ciscovni.com/vni_forecast/index.htm 8 9. Sketching
on many devices HTML5 1.4 devices per person by 2016 1 Design
interfaceso Diverse contexto Weight, screen typeso E-paper?1 -
CISCOs Visual Networking
Indexhttp://www.ciscovni.com/vni_forecast/index.htm 9 10. Devices
10FPS 25FPS 45FPS15FPS21 FPS10 11. Benchmark11 12. Why? Developers
would know what to doo Respond accordinglyo Keep the refresh rate
low Discard some deviceso Activitieso User profiles 12 13.
Experiment What is the FPS rate at which the users start toperceive
the system as too slow? Three phases Draw squares and grade the
speed. 13 14. Subjects 35 users recruited around the campus. o 16
women, 19 men o Avg. 28 years old Different nationalities Different
fields of expertise o Biology, Psychology, Computer Science,
Management, etc. 14 15. Material Wacom Cintiq12o 75 Hz (upper limit
of 75 FPS) MacBook pro 2.9GHz http://exp.gambit-sketch.appspot.com
(be nice) 15 16. Two groups 16 17. 1st phase A vs B comparison Are
the responserates different? Goal: find out if usersperceive small
orlarge differences17 18. 1st phase18 19. 1st phase19 20. Results:
1st phase 20 21. Results: 1st phase Not conclusive21 22. 2nd phase
Likert scale grading How happy areyou with thisresponse rate? Goal:
find out whenthe users start tograde as bad andreally bad 22 23.
2nd phase23 24. Results: 2nd phase 24 25. Results: 2nd phase 25 26.
Results: 2nd phase 26 27. 3rd phase Active selection of apreferred
response rate What is the minimum inyour opinion? Goal:
cross-validate the2nd phase 27 28. Results: 3rd phase 28 29.
Findings The range below 20 FPS was rejected by users; The
difference between grades is not significantabove 24 FPS No
conclusive evidence that subjects perceiveddifferences of 2, 5 and
10 FPS when testing pairs ofrates 29 30. Next steps Writing
activity Specific types ofprofessionals o Designers o Architects o
Non-drawing professionals 30 31. Thank you
[email protected] @ugosan 31
