4.0 Loop Control System - Basic Concepts
You can define a random or sequential loop of image frames, and set the
display time (dwell rate) for each frame in the loop.
Loop Bounds and Sequences
Image frames in the image window are like slides in a slide projector
carousel, in that any frame can be brought easily into view or looked at in
any order, but you cannot look at more than one at the same time in the same
A loop has beginning and ending frames called loop bounds. When you
start McIDAS, the loop bounds are set as frames one through
the total number of frames. If you log on to McIDAS and initialize
the workstation, the loop bounds are one through one-half the
total number of image frames. You will use the commands
LB and LS to set loop
sequences which can be sequential or random.
When you define loop bounds, you also create opposite loop bounds.
Each frame has an opposite frame that is half the total number of frames away. For example, on a session with ten frames,
frames 1 and 6 are opposite, frames 2 and 7 are opposite, etc. The single letter command O toggles between a frame and its
opposite, which is useful for comparing images.
The dwell rate is the amount of time each frame is displayed during
automatic looping. The default dwell rate is nine units for the
first frame and six units for the remaining frames. In McIDAS-X, one
unit is appoximately 1/15th of a second; the fastest dwell rate is
1/15 of a second (1 unit), though some workstations will not be
able to sustain that rate.