The iHelmet: An AR-enhanced Wearable Display for BIM Information - Mobile and Pervasive Computing in Construction - page 160

Figure 8.8 Relationship between screen dimensions and the real environment

where S p is the screen's dimension in pixels and S i is the screen's dimension in
inches.
Secondly, we need to relate the distance between the touching point and the two
edges of the view unit displayed on the screen to the real environment. From the
proportion P S calculated from Equation 8.1, the distance between the touch point
and two edges of the view unit can be converted into a distance in the real
environment, as shown in Equation 8.2:

D r ¼ P S D v ð 8 : 2 Þ

where D r is the distance in real environment and D v is the distance between the
touch point and the two edges of the view unit. The relationship between the
parameters in Equations 8.1 and 2 is shown in Figure 8.8.

Projection Range

As indicated in Figure 8.7, the small rectangle represents the projection range. The
dimensions of the rectangle change according to the position of the user. Equation
8.2 and the throw ratio of the projector were used to change the dimensions of the
projection range. The size of the projection range will increase with distance and
decrease with greater proximity. Though this rectangle is small, users will likely be
able to find a suitable place to project the information.

8.3.3 Manipulation module

The manipulation module can simplify the process of browsing information so that
users can browse and diagnose problems in the information efficiently. Hence, this
research proposed four control types for different purposes: Single Tap, Slide,
Double Tap, and Gesture (Figure 8.9).