Traditional sketching aids rely on the physical production of templates or stencils which is particularly problematic in the case of larger formats. One possible solution is 2D virtual tracing using a virtual template to create a physical sketch. This paper evaluates a mobile phone as a 2D virtual tracing tool by comparing three tracing methods: (i) a traditional tracing method with a printed template, (ii) a virtual tracing method Static Peephole (SP) in which the virtual template is manually adjusted to a physical contour by drag and pinch gestures, and (iii) a virtual tracing method augmented reality Magic Lens (ML) in which template is projected on the physical object such as paper hence navigation is possible through physical movement of the mobile device. The results show that it is possible to use mobile phones for virtual tracing, however, ML only achieved comparable performance to SP mode and traditional methods continued to be quicker and preferred by users. Paper: http://link.springer.com/chapter/10.1007%2F978-3-319-44805-3_22

1. Using a Mobile Phone as a 2D
Virtual Tracing Tool: Static
Peephole vs. Magic Lens
Klen Čopič Pucihar, Matjaž Kljun, Paul Coulton

2. There are many people who like to create and
make things with their hands.
These people to create all sorts of paintings.

3. Or sawing their own clothes.

4. Or build models from balsa wood such as
houses

5. Or Planes.
In the process of making these things they are
regularly faced with the taskk of transcribe
inforrmation from one object to another.

6. For example when building minature plane
model. Creator needs to transcribe designs
from blueprint to balsa wood prior to cutting
(transcription is done from blueprint to balsa
wood).

7. Or, when they saw their own cloths, they need to cut the material prior to sawing,
hence the cutting plan needs to be transcribed to the fabric (transcription is done
from sawing pattern to fabric).
Or you are not very skilled at setting the correct perspective or porpotions so you
use existing designs to help you set out drawing plan (transciption is done from
printed template to semi transparent surface such as tracepaper.
All this tasks requre the creator to transcribe infromation from one object to
another. So lets look now at how people actually do these things.
There are many ways in which one can transcribe information from one object to
another. For example skilled artists can achieve this transcription by mapping their
observations to this new layer. This is ok for artistic elements, but not very effective
for istuations where correct size of the object is esential for sucesful end result.

8. An alternative options is to use template
technique. Which can work by placing a
template bellow a semi transparent paper
(trace paper). Or by putting and indigo paper
bellow template. At the place of exerted
pressure, indigo will leave a mark on the
underlaying surface.
Traditional Sketching Aids

9. Alternative to templates are stenciles which
are cut out templates that let users follow the
edges in order to transcribe the information.
In both cases one needs to production such
templates or stencils which is time consuming,
difficult and limiting specially in case of bigger
formats. For example how many of you have
access A0 printer or printer bigger than A3?

10. One possible solution is virtual tracing using
virtual templates.
Virtual tracing is a method of transcribing
instructions from virtual template shown on
mobile device screen onto underlaying surface
(paper) . The mobile device renders a virtual
template image, such as a contour line, onto
device screen together with a live video stream
of the drawing surface.
One possible solution is virtual tracing using
virtual templates.
Virtual tracing is a method of transcribing
instructions from virtual template shown on
mobile device screen onto underlaying surface
(paper) . The mobile device renders a virtual
template image, such as a contour line, onto
device screen together with a live video stream
of the drawing surface.
Video

11. This paper evaluates a mobile phone as a virtual tracing tool and compares it
with traditional sketching aids. We compare 3 interfaces:
a traditional tracing method with a printed template,
a virtual tracing method Static Peephole (SP)
a virtual tracing augmented reality Magic Lens (ML)
Compared to traditional methods, virtual tracing has a clear advantage in that it
does not require the physical production of sketching aids, which is particularly
problematic when one desires to draw on large formats.
In case of virtual tracing, the drawing size is not limited; although, when the
drawing surface does not fit on the screen, one needs to move the device in
order to reveal the unfinished drawing surface.
The core challenge is alignment of the virtual template with what has been
drawn thus far!
- In SP interaction the user uses touchscreen gestures to align virtual contour
with wath has been drawn this far.
- In ML mode the the alignment is done automatically as long as it is possible
to track the camera pose in relation to the drawing surface. As the alignment is
done at each rendered frame, the user does not need to keep the device
perfectly still while drawing a particular segment and may hold the phone in
hand. (As you saw in demo video.)
However, the ML is highly dependent on camera tracking which may diminish
sketching experience, particularly as it is difficult to implement robust and
accurate camera tracking on a blank drawing surface where the hand holding
the pencil can occlude segments of the scene.
Additionally, when compared to traditional sketching aids, both virtual tracing
methods require the user to look through the phone while sketching and only
show a segment of the image being drawn at the time.
Template Static Peephole Magic Lens

12. Research questions
• How effective are phones in supporting user
sketching through virtual tracing?
• Do users find the advantage of the ML useful?
• Can users’ draw whilst holding the ML in hand?

13. To answer these question we run a user study
where users were asked to sketch a cartoon
character using the aformentioned three
different method. Template, SP, ML.
We had 7 participatnts aged between 23 and
45 (3—employed, 4— students) coming from
verious backgrounds (1), architecture (1),
computer science (3), medicine (1) and
mechanical engineering (1).
Participants were asked to complete the task
as quickly and as accurately as possible. Each
participant complete three drawings, one with
each method.
Task

14. Data Collection
• Drawings
• Task time
• QUIS (overall reactions)
• Open ended questions:
• Rank interaction modes and justify their decision
• Highlight the most difficult part of the task

15. We took 3 drawings each participants finished
and ranked them from best to worst. This was
done by two researchers independently.
Looking at quality ranking results on the right
we can see that the differences are not very
big, however the Template method ranked
best followed by ML and SP method.
Quality
Conclusion:
•It is possible to use mobile phones for virtual tracing.
•Virtual tracing whilst holding phone in hand is possible.

16. Looking at time it is obvious that traditional
sketching method is the fastest, whilst there is
only small advantage of ML over SP.
This is surprising as in SPparticipants had to
manually align the sketch every time they
moved the phone.
Time
Conclusion:
•Users are very good at manually
aligning the virtual contour with what
has been drawn this far.
•Automatic alignment using a marker is
not good enough.

17. The same trend is shown by QUIS scores.
Template is marked as best, whilst there is
only small difference between ML and SP.
Supporting our previous conlcusions.
QUIS

18. Rank
Looking at ranking
results the same trend
emerges.
So now we are left with
observational results.

19. Observational results
• Participants adjusted the stand or held the phone at a distance of 17-22
cm.
• When drawing, participants always looked at the paper through the
phone keeping the pencil within the cameras’ field-of-view.
• Participants looked at the paper to see how they were progressing.
• In SP, participants drew all instructions within the screen segment,
including those at the very edge of the screen.
• In SP mode participants expressed the need for a minimap.

20. Conclusion
• It is possible to use mobile phones for virtual tracing,
although, traditional methods continue to be quicker.
• Virtual tracing whilst holding phone in hand is possible.
• ML only achieved comparable performance to SP
mode. This coupled with users’ dislike of the marker
suggest that currently available tracking solutions are
not good enough.

21. Future work
• Look into ways of detecting what has been drawn thus
far.
• Run a study with more participants to get conclusive
results.
• Explore the use of a stand in the context of the ML
interaction mode.
• Evaluate virtual tracing using virtual mirror metaphor.
• Look into ways of supporting transcribing 3D
information to objects (sculpturing aids).

22. Thank you for your time.
Questions/comments?
matjaz.kljun@famnit.upr.si
klen.copic@famnit.upr.si
p.coulton@lancaster.ac.uk