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SETTING TRACKING PARAMETERS
The real-time screen features interactive control of the following tracking parameters:
Sample rate - This is the number of readings per second that the system is taking. A
value of 24 is the maximum for a tracking area of 10 x 6 m (33 x 20 ft). Refer to
chapter 8 for an in-depth discussion of sampling rate issues and a formula to calculate
the maximum rate for your stage.
Samples averaged - This is the number of readings that the system will average. The
more samples averaged the "steadier" and more precise will the tracker data be, the
downside being that the response is slower. Conversely, fewer samples averaged means
faster response but more "jittery" tracking.
Anchoring radius - Sometimes it is convenient to "anchor" a tracker so that small
movements by particularly active performers do not have an effect on followspots. The
anchoring radius is the distance in centimeters (or inches if that's your choice) that a
tracker has to move before resuming control of media. For a followspot with a 1.5
metre diameter set your anchoring radius to about 40 cm. Note that anchoring only
applies to automated followspots.
Pulse volume - This tells the MLD how loud you want the ultrasonic pulses to be. In
most cases the default 33% is ideal. Only if your system is set-up in very loud
environments, such as rock shows, will you need to bring this value up a little. Please be
aware that as you increase the volume you will increase your chances of getting
ultrasonic echoes which might degrade performance.
Cymbal rejection - This parameter allow you to set how much filtering to apply to
eliminate "background" ultrasonic noise sources, such as cymbals. The default value of
50 is ideal, setting this higher might begin to eliminate some MLD pulses as well.
Prediction time - The MLD software can analyze how the performers are moving and
try to "guess" where they will be in the future. This is useful because followspots may
linger due to tracking, DMX and fixture lag. This parameter tells the MLD how much
time into the future you want it to predict. Normally, setting this to 0.25 (a quarter of a
second) will be acceptable in most cases.
Prediction sensitivity - This parameter tells the MLD how much you want to rely on
the prediction. Use this parameter keeping in mind the following trade-off: the more
sensitivity the faster the MLD will accept the prediction data but the more "jittery" will
the followspots be. A lower setting yields a smoother following, but will also increase
the time the filter takes to lock onto you if you stop or otherwise change you
direction/velocity rapidly. The default setting of 30 is ideal for most cases.
Side note: the best way to understand the relationship between the prediction parameters and
the quality of tracking is to use the system in "Mouse Test" mode and see the effect that
variation of the parameters does on the simulated tracker (the dot on the screen).
IMPORTANT NOTE: prediction is particularly useful when your sample rate is low, for
example in large stages, or when your performers run very fast. If you want to turn it
off, simply set both prediction parameters to zero.
MLD manual 1.1
Page 67
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