  A particular measure to evaluate a head-mounted display (HMD) based
experience is the state of feeling present in virtual reality. Interruptions of
a presence experience - break in presence (BIP) - appearing over time, need to
be detected to assess and improve an application. Existing methods either lack
in taking these BIPs into account - questionnaires - or are complex in their
application and evaluation - physiological and behavioral measures -. To
provide a practical approach, we propose a post-experience method in which the
users reflect on their experience by drawing a line, indicating their
experienced state of presence, in a paper-based drawing template. The amplitude
of the drawn line represents the variation of their presence experience over
time. We propose a descriptive model that describes temporal variations in the
drawings by the definition of relevant points over time - e.g., putting on the
HMD -, phases of the experience - e.g., transition into VR - and parameters -
e.g., the transition time -. The descriptive model enables us to objectively
evaluate user drawings and represent the course of the drawings by a defined
set of parameters. An exploratory user study (N=30) showed that the drawings
are very consistent, the method can detect all BIPs and shows good indications
for representing the intensity of a BIP. With our method practitioners and
researchers can accelerate the evaluation and optimization of experiences by
evaluating BIPs. The possibility to store objective parameters paves the way
for automated evaluation methods and big data approaches.
