Dataton WATCHOUT User's Guide

Overlapping Display Areas
Using projectors, you can build larger, seamless image areas by allowing each
projector to overlap its neighbors. The amount of overlap is usually referred to
in terms of its percentage. With a 50% overlap, half of the projected width or
height intrudes into the adjacent projection area. In general, the larger overlap
you use, the more seamless the image will appear. Acceptable overlap ranges
from 20 to 50 percent. Due to the consistency and long-term stability of
modern computer projectors, you can often apply a smaller amount of overlap
in WATCHOUT than you could with traditional slide-projector, multi-image
techniques.
In WATCHOUT, you specify the amount of overlap simply by locating the
screens at the corresponding positions, specified in pixels. The Stage window
has a coordinate system with its origo in the upper left corner. Place the leftmost/topmost
display slightly into the Stage window; eg, at position top: 100
and left: 100. This allows you to place images outside visible display areas, eg,
to fly them in.
You continue to calculate the screen positions from here, taking the desired
amount of overlap into account. Assuming that each projector displays 800 by
600 pixels, the first display extends from the horizontal position 100 through
to 900 (100 + image with). A 30% horizontal overlap out of 800 pixels is
800 x 0.30 = 240 pixels, so the second display area will start at horizontal
position 900 – 240 = 660 pixels.
Chapter 5: Planning 53