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Making Smooth Position Fades for Live Shows with the X1
2/12/05 – Roadie Steve
Background
I have had several X1 users ask me for advice on how to handle a particular situation. Imagine
you are doing a live show, but you know very little about the performers and there is no rehearsal.
Now, imagine that you have 6 moving heads on the floor, three upstage left, three upstage right.
Ideally, you would like to have some pre-programmed positions, along with some preprogrammed
colors and effects, then mix and match them in real time in response to the
performance on stage.
Basic Setup
Since the X1 sums cues ‘additively’, something like this is easy to setup on the X1’s Submasters.
So, imagine you start by creating a new cue (#1000, Fan Intensity). You add all six fixtures,
select them, open their shutters, and bring their dimmer channels up to full.
Next, you then assign Cue #1000 to Submaster 1. And you clear Cue #1000 from the XY
Crossfaders (assign cue #0, or use the ‘Clear XY assignments’ option in the Submaster menu
(v1.1)).
Submaster 1 now fades the intensity up and down for your fan lights. You can adjust the fader
onscreen, or using an external DMX console. Since the intent is to run the show live, we will
assume that you have at least an inexpensive DMX console available.
After bringing Submaster 1 to full (100%), you create a new Cue (#1010, Columns) and add all
six lights to it. In this cue, you leave the shutter and dimmer untouched, but you place all six
lights in their home, or straight up position.
Note – once you have selected (blue border) the position control, pressing the HOME key will
set pan and tilt to their exact mid points.
Next, you duplicate this new cue (#1011, Straight) and adjust all 6 lights so that they are making a
fan straight out over the audience’s head. You then duplicate again (#1012, Cross) and adjust
your fan so that the beams are crossing each other out over the audience’s head.
Remember, you can adjust position multiple ways, clicking and dragging in the control, clicking
and holding the arrow buttons on the border, mouse scroll wheel and CTRL + scroll wheel to tilt and
pan, and scroll wheel click to capture and release for ‘tracking’ mode. You can also adjust
multiple fixtures at the same time.
You can now assign these new cues to Submasters 2-4, and clear them from the XY faders.
You now can select one of three positions, and adjust intensity using 4 faders on your console.
You can now take this idea further. You create four additional cues (#1020 Blue, #1021 Red,
#1022 Magenta, #1030 Circles).
In the first three of these cues, you select a color, and perhaps a gobo and focus, but you leave
position, shutter, and dimmer untouched. In the last of these cues, you turn on the Circle effect
for all six fixtures, and select the ‘Reverse’ option for the three fixtures on stage right.
Once you have mapped these new cues onto Submasters 13-16, and cleared them from the XY
faders, you will have the following:
You now adjust intensity, mix and match positions and colors, and even mix in a circle effect, all
in real time from your external console. You could even extend this basic technique; for example,
you could have a fader which controls Effect Gain, and another that adjusts Effect Speed, or
faders for color spins and other fixture effects. You can also use Presets to extend the number of
base cues available for mixing (ex. imagine if the first five presets all had the same Cue
assignments, except for Submaster 16, which was changing from ‘Circles’ to ‘Figure-8, etc.)
The Problem
Everything above works as expected. However, most users encounter one problem, when they
try to fade between two position cues (ex. #1010 and #1011) using faders on an external console,
the motion is often jerky.
The reason for this is basically two fold. First, it is physically hard to move the two faders at the
same speed and proportions in opposite directions – especially if the faders are of so-so quality.
Second, the faders themselves may not be linear – that is a 90% setting on one fader and a 10%
setting on the other may actually be resulting in 80% and 4% on the DMX output.
Solutions
There are actually quite a few different ways to tackle this problem. I will list several, along with
some pros and cons, below. Sometimes it is helpful to combine the following techniques.
Approach 1 – Practice…
Believe it or not, it is possible to get nice fades on most boards. One technique that seems to
help most people is to use two hands and lead with the position cue you are going to. That is,
start fading the destination position up before you start fading the current position down.
Pros:
- Fade time is flexible
- The ‘curved’ track that the
lights take can be visually appealing
- Since the fixtures are very
responsive, you can shake faders for down-and-dirty
ballies
- You can be annoyingly smug the first time someone else tries it
Cons:
- For most mortals, it takes
two hands, so it is hard to combine the fade with
other changes
- Fades are never truly linear
(shortest path to new position)
- It requires some operator practice and experience
Approach 2 – Use a Two Scene Board
Many low cost DMX consoles offer a two scene mode. For example, the festering hunk of junk I
use for testing (whose manufacturer will remain unnamed, since anyone who would sell such a
crappy product would not hesitate to send thugs to my house) can operate as a 1 scene, 24
channel console, or a two scene, 12 channel console.
If I put Submasters 1 and 2 at 100% in the first scene, and Submasters 1 and 3 at 100% in the
second scene, the crossfade (using the scene select fader) between Cue #1010 and #1011 is
very smooth, and the intensity remains unchanged. That is, of course, unless I press firmly on
the upper right corner of the console, then all the channels randomly oscillate between 10% and
45%...
Pros:
- Fade time is flexible
- Fades are consistently linear
Cons:
- Requires a two scene board
- Scene ‘setup’ takes time
Approach 3 – Slow Down Motor Speed in the Position Cues
Most moving fixtures have a pan/tilt speed control of some kind. Although the exact behavior
varies from fixture to fixture, it is normally one of two arrangements. Sometimes the control
represents fastest motor speed at the bottom (0%) and slowest motor speed at the top (100%).
Other times 100% represents the fastest speed, 1% the slowest, and 0% fastest again.
Either way, you could adjust the control in your position cues so that you get a ‘generic’ (say
roughly 3 second) fade when you ‘bump’ (flash buttons or quick fader changes) between them.
Pros:
- You can ‘fade’ with bump
buttons
- With most fixtures, the motion is very smooth
Cons:
- Speed is fixed, so the fade
time between any two positions is fixed
- If you are mixing fixture brands and models, fade times may not exactly match
Approach 4 – Variation on 3, put Pan/Tilt Speed in a Separate Cue
Much the way you originally split out color, position, and intensity, you could create a cue that just
adjusts PT Speed to the highest level you want to use. You could then assign this Cue to a
Submaster and then adjust the Submaster to vary the speed when you ‘bump’ between position
cues.
Approach 5 – Use an Event List
Examine the following Event List:
Each position Cue appears three times, once with no fade time, once with a 3 second fade time,
and once with a 7 second fade time. If we change from “Internal” mode to “Step” mode (either
using the Run menu or the mode selector next to the time display) a ‘next’ arrow can be manually
set. Just double click in the gray area to the left of the event you wish to designate next or right
click and select ‘Set Next Marker’ from the popup menu. In version 1.1 you can also use
keyboard shortcuts (see the Edit menu).
Above, the next pointer is set to ‘Cross’ with a three second fade time. If is pressed,
or the play button in the toolbar is clicked, the fade will occur automatically.
This basic process, select destination and speed, then hit (or select play) to execute,
can be repeated over and over.
There are several things worth noting about this approach. First, in Step Mode, each event list
maintains its own Current and Next pointer. Unlike Timecode and Internal mode, the Lists do not
have to run concurrently. This can be used to manage different groups of fixtures separately.
For example, List 1 is the Fan fixtures above, List 2 could manage downstage overhead fixtures.
Since they are in different lists, they can be moved and positioned separately during the show.
Second, fades do not have to be linear. You can split the fade time for an event to recreate the
‘curved’ transitions that we saw in Approach 1.
Pros:
- Fades are consistent and
smooth
- Many positions can be
pre-programmed
- More Submasters are available for colors, gobos, and effects
Cons:
- Fade times are essentially
fixed
- Mouse or keyboard must be used at showtime
Additional Approaches
Version 1.1 offers some additional features that could potentially be used. For example, the XY
Crossfaders are available via the extended DMX Input Protocol. Submasters can also be
triggered with fade times from other sources (ex. the MIDI sample for the Automation API).
However, I have found some combination of the above approaches to be the most useful in
typical show situations.
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