Theatre Design & Technology - Spring 2017 - Public - 22

Front wall elevation of video wall, showing numbered displays (directly above), and tech rehearsal (top).
Photos by Megan M. Reilly.

Pi Wall Budget
Qty

Item

Cost
per unit

Total cost

Raspberry Pi 2 Model B Project Board, 1GB
RAM, 900 MHz Quad-Core CPU

$48.79

$1,122.17

Tontec New Raspberry Pi 2 Case

$6.99

$160.77

8GB microSDHC Class 4 Flash Memory Card

$4.29

$98.67

Micro USB Power Wall Supply Charger

$7.99

$183.77

HDMI to DVI adapter cable

$7.99

$183.77

Displays - amount spent total

$472.91

Ethernet switch - used Playhouse's inventory

$0.00

Ethernet cable - used Playhouse's inventory

$0.00
TOTAL
COST:

theatre design

& technology

$2,222.06

S p r i n g 2 0 1 7

munities of users and programmers are willing to help
first-timers. It requires some set up and programming
time-building each computer, installing the operating
system, and configuring the software to the specific video wall layout in question. Each display is connected to
its own Raspberry Pi, and a "master" Pi in turn controls
them all. Once set up, video files can be sent from the
master computer to the wall, and each Pi divides up the
image and displays only its portion of the whole.
The online community surrounding PiWall is
one of its strengths. According to Alex Goodyear, the
Water by the Spoonful production was the largest noncommercial PiWall he knew of at that time; PiWall was
developing a commercial version and working on a few
productions that had more than 300 displays.
The first step in considering PiWall as a solution
was to run a small test. The test required purchasing
three Raspberry Pi computers on Amazon (3 Raspberry
Pi 2 Model B Project Boards, 1 GB RAM, 900 MHz
Quad Core CPU plus Tontec cases, 8GB memory cards,
power supplies and adapters) and setting up a three-display PiWall in Landazuri's office as a "proof of concept."
The video files are played on the wall by executing shell
scripts on the master computer. Combining theatrical
knowledge and software with the open source PiWall
enabled the team to troubleshoot control scripts during
this test. QLab 3 was used to execute the shell scripts,
since typing out an entire command at a prompt for every "go" given by a stage manager wasn't a feasible solution for an operator during a performance. QLab 3
provided the perfect solution because it allows a user to
add a "script" cue rather than a video, sound, or other
typical type of cue. The script cue in QLab 3 contains
a tab where the user enters the script QLab needs to
execute upon "go." All the shell scripts could then be executed without having to enter a command at a prompt.
Once the Playhouse team saw that this solution could
work, assembly began on the other 20 computers.
Each SD card was installed with the software found
on PiWall's website, making them the "hard drives" for
the Raspberry Pi computers. Each Pi computer was assigned a unique IP address within the software that in
turn reflected the number assigned to its "tile." In order
to tell each Pi where its particular tile was located, a grid
was placed over a front elevation drawing of the wall,
which determined the x and y coordinates for the top
left corner of each display. This was not done using any
method PiWall suggested and instead drew again upon
standard theatrical knowledge. Scale drawings were created in Vectorworks based off the set designer's Sketchup
model, and a grid of two-inch by two-inch squares was
laid on top of a front elevation of the wall. The coordinates (0,0) became the top left corner of the wall itself,
and so display #1, which was the closest to that corner,
started at (2,2). These coordinates were then installed
along with the rest of the software onto the Raspberry
Pis, and each unit was carefully labeled on the outside.

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