anthonyn / CosmicPraise

Cosmic Praise 52' tower lighting & associated electronics

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Cosmic Praise

Simulator and lighting code for Cosmic Praise, a fifty-two-foot-tall cosmic-ray detector covered in LEDs.



  1. Install dependencies
sudo pip install colormath 
  1. Run the simulator (pre-built for OSX, Ubuntu 14.04 32-bit, and Linux Mint 64-bit; for other platforms, you can get the source and build yourself from our OPC fork here:
simulator/osx-10.9/gl_server layout/cosmicpraise.json
  1. Run the client code to send pixels to the simulator:
python client/python/ -l layout/cosmicpraise.json -f 60 --sim
  1. The client will start running an effect, and you should see it running in the simulator. Go back to the client window and hit Enter to switch to the next effect. (More sophisticated show control is available via OSC, see below.)

About the system

The tower structure is covered with 150 meters of WS2812 LED strip and 49 Philips Color Kinetics RGB fixtures; over 4600 individual pixels. The strips are run by LEDscape running on Beaglebone Blacks receiving OpenPixelControl (TCP), and the CK fixtures are powered by Ethernet-enabled CK power suppies communicating over Kinet (UDP).

We've modified the OpenPixelControl Python client to speak Kinet as well as OPC, and extended the OpenPixelControl layout and simulator to model and simulate the features of the Cosmic Praise tower, including flat surfaces of illumination representing the color wash targets of the Color Kinetics fixtures.

section lights
base 24 ColorBurst fixtures, about 12' off the ground, pointing down at the vinyl base cover, which is painted with techniques that react well to color-changing light.
middle 24 roughly 6 meter WS2812 LED strips crisscrossing along with the steel beams of the tower. Each strip is split into a 4.77m lower section and a 1.33m upper section, just as the steel structural beams are.
railing 12 CK Fresco coves with two fixtures each, just below the handrail, illuminating the woodcut panels of the tower top railing.
roofline 6 2.33m WS2812 strips ringing the roof of the tower top
spotlight A 300W LED spotlight on a rotating bearing above the tower roof
spire 16 1m WS2812 strips making an 8' antenna atop the tower roof.

How to contribute to Cosmic Praise

  1. Fork the Cosmic Praise repo to your own account.
  2. Create a new file in client/python/effects by copying to <your name>.py.
  3. Define your effect function (see next section) and put its name in the __all__ list.
  4. Test your code in the simulator and revise. Commit it, then make another one!
  5. When they all look beautiful, create a pull request on Github to contribute your changes back to the main repo.

How to write LED effects

You can see the existing effect library here:

The simplest possible effect would be to just color every pixel in the tower the same color (in this case, hue 0 in the default palette, or red.)

def simplestExampleEffect(tower, state):
    for pixel in tower:
        tower.set_pixel(pixel, 0)

Slightly more complicated is to color each pixel differently with some math based on its cylindrical coordinates, and the animation time:

def verySimpleExampleEffect(tower, state):
    for pixel in tower:
        tower.set_pixel(pixel, pixel['theta'] / twopi, state.time % 0.5)

An effect is just a function that takes two arguments, tower and state, and calls tower.set_pixel(pixel, chroma, luma) on whatever parts of the structure it wants to light up. tower.set_pixel expects a pixel item from an iterator, plus two values: a "chroma" and a "luma" value. These will be mapped to the current palette of the sculpture, so we can overlap or sequence multiple effects and still achieve the effect of a unified aesthetic object.

chroma and luma should both range from 0.0 to 1.0. You can think of chroma as indexing through an imaginary watercolor paintbox of unknown size, with 0.0 the left side of the box and 1.0 the right side, and luma as making it full strength at 1.0, or watering it down to transparent at 0.0.

There is also a tower.set_pixel_rgb(pixel, rgb), which expects a RGB tuple of values 0.0-1.0, for effects that must be a specific color, whether for debugging or for a specific aesthetic need. But we encourage you to use tower.set_pixel unless absolutely necessary.

The tower object also provides iterators over the entire structure, or a certain part, like tower.railing or tower.spire. Iterating over these generators gives you pixel items, each of which is a dictionary with information about the pixel including its (x,y,z) coordinates in 3D space, its (theta, r, z) coordinates in cylindrical 3D space, its strip index and address, etc. So you can color different parts of the structure with different techniques:

def simpleExampleEffect(tower, state):
    # make the base blue
    for pixel in tower.base:
        tower.set_pixel_rgb(pixel, (0, 0, 1))
    # make the railing red
    for pixel in tower.railing:
        tower.set_pixel_rgb(pixel, (1, 0, 0))
    # fade the tower middle from blue to red
    tower_height = 15.0
    for pixel in tower.middle:
        s = pixel['z'] / tower_height
        tower.set_pixel_rgb(pixel, (s, 0, (1 - s)))
    # and spin a yellow line clockwise around the clockwise tower diagonals
    n = int(state.time % 12)
    for pixel in tower.clockwise_index(n):
        tower.set_pixel_rgb(pixel, (1, 1, 0))
    # make the roofline and spire flash green
    for pixel in chain(tower.roofline, tower.spire):
        tower.set_pixel_rgb(pixel, (0, state.time % 1, 0))

The tower object provides the following methods and generators at the moment:

method use
tower.set_pixel(pixel, chroma, luma) Set the color of a pixel according to the current global palette, where chroma and luma range from 0.0 to 1.0. This is the preferred method, for unified color blending across multiple effects.
tower.set_pixel_rgb(pixel, rgb) Set the color of a pixel to a RGB tuple, each from 0.0 to 1.0. Use only if strictly necessary.
basic generators iterates over
tower or tower.all every pixel, in arbitrary order
tower.spire all the pixels in the spire strips, starting at the bottom of the spire and proceeding counterclockwise in each ring
tower.spire_index(n) where n=0 through 15, all the pixels in one specific ring, starting at the bottom of the spire and proceeding counterclockwise in each ring
tower.roofline all the pixels in the roofline strips in counterclockwise order
tower.railing the 24 railing cove lights in counterclockwise order
tower.base the 24 colorburst fixtures illuminating the base section vinyl mural, in counterclockwise order
tower.middle, tower.diagonals the diagonally crisscrossing strips on the top two steel sections of the tower, one strip at a time, in counter-clockwise order, pixels ordered from top to bottom
tower.diagonals_index(n) where n=0 through 23, a specific diagonal strip, pixels ordered from top to bottom
tower.spotlight Iterates over just one pixel: a NINE THOUSAND lumen 300W LED spotlight, the kind they use on the Empire State Building and the Zakim Bridge. It's represented in the simulator as a single dot, but it will actually be spinning a tight beam across the playa. Unless we have enough time to put together a network control system, it will probably be spinning at roughly 60-70rpm. If conditions line up right, the beam should be visible like a laser in the dusty air. What crazy things can you come up with to do with it?

The above generators cover the basic parts of the structure, but we have additional fancier generators just for the diagonal grid on the middle of the tower, which is sort of our main play surface. See addressOrderTest, diamondTest, and lightningTest for a demonstration of the fancier generators.

fancy generators iterates over
tower.clockwise only the clockwise middle diagonal crossing strips
tower.counter_clockwise only the counter-clockwise middle diagonal crossing strips
tower.clockwise_index(n), tower.counter_clockwise_index(n) where n=0 through 11, a specific diagonal strip of a certain direction, pixels ordered from top to bottom
tower.diagonals_index_reversed(n), tower.clockwise_index_reversed(n), tower.counter_clockwise_index_reversed(n) Same as above, but the sequence and the pixel order starts at the bottom. This is not the same as calling reversed(tower.diagonals(n)), because the diagonals are interleaved in a different order at the top and bottom of the tower.
tower.diagonal_segment(index, row) one segment of the diagonal grid, from the strip index 0-23, where row = 0 is the topmost segment, row = 5 is the bottom-most.
tower.diagonal_segment(index, toprow, bottomrow) an arbitrary line segment on the diagonal grid, from the strip index 0-23, beginning at row toprow (0-5) and ending at row endrow (0-5), inclusive.
tower.diamond(row, col) Four sections of diagonal strip in a diamond pattern. Row counts from 0 to 4 down from the top, column is from 0 to 23 counting counter-clockwise.
tower.diamonds_even evenly spaced non-overlapping diamonds on rows 0, 2, 4
tower.diamonds_odd evenly spaced non-overlapping diamonds on rows 1 and 3
tower.diamonds_even_shifted, tower.diamonds_odd_shifted same as above, but rotated slightly
tower.lightning(start, seed) a branching path down the tower middle, similar to a lightning bolt, where start=0 through 23, the starting location of the bolt, and seed is a value from 0.0-1.0 that determines the branching decisions.

The state object provides:

property purpose
state.time the current time, to drive animations a list of recent spark chamber events. Each event is a tuple of (event time, power level). Power levels are currently always zero until we get the ADC-PIC-Arduino-MIDI pipeline sorted. You can simulate spark chamber events by creating a virtual MIDI source or plugging in a hardware MIDI device, restarting the client, and sending MIDI note on messages (note number not important.) This feature requires that the python-rtmidi be installed, see below.
state.random_values a list of 10,000 pregenerated random numbers, consistent across frames
state.accumulator an effect-defined accumulation value, useful for feedback effects

Effect Parameters and OSC

Effects can define additional named arguments after the (tower, state) arguments. Any named arguments will be slurped up into the OSC server and exposed as endpoints for timeline or interactive control. This will allow us to get a lot more variation and interest out of simple effects.

def cortex(tower, state, sVert=0.0, sHorizon=0.0, spiralAltPeriod=4.0):

In order to use the OSC features, you'll need to install the pyOSC module.

pip install pyosc --pre

Running the Client Using Pypy and Python Virtual Environments

Pypy is a new version of the Python language tools that is substantially faster that the default implementation. Virtual environments provide a nice method for keeping python projects and their dependencies locally managed and seperate from the system. Running pypy inside a virtual environment is the recommended method of running the Cosmic Praise python client.

  1. Install virtualenv if it isn't already on your system:
$ sudo pip install virtualenv
  1. Install pypy. You may be able to install it directly from your system's package manager (e.g. sudo apt-get install pypy or brew install pypy.) If not, you can download it from and link it into /usr/local/bin.

  2. Create a new environment for Cosmic Praise and install the required libraries.


 $ virtualenv -p /usr/local/bin/pypy $HOME/local/cosmic-praise
 $ . $HOME/local/cosmic-praise/bin/activate
 (cosmic-praise)$ pip install colormath
 (cosmic-praise)$ pip install git+


$ virtualenv -p /usr/bin/pypy $HOME/local/cosmic-praise   
$ . $HOME/local/cosmic-praise/bin/activate
(cosmic-praise)$ pip install colormath
(cosmic-praise)$ sudo apt-get install build-essential pypy-dev git
(cosmic-praise)$ pip install git+
  1. Now you can run the Cosmic Praise client in pypy to get much better performance:
pypy client/python/ -l layout/cosmicpraise.json -f 60 --sim


To receive MIDI events from the spark chamber, the python-rtmidi module is required. If you don't need to use or test this feature, you can ignore this section.

  (cosmic-praise)$ sudo apt-get install libasound2-dev libjack-dev
  (cosmic-praise)$ sudo pip install python-rtmidi --pre

Ubuntu users may need to build python-rtmidi from the source distro, see the troubleshooting section below.


Segmentation fault running simulator

Make sure you have typed the path to the layout .json file correctly. If all else fails, try building your own copy of the simulator from

Pypy client fails with an "ImportError: unable to load"

You need to reinstall python-rtmidi linked with libc++.

  1. (cosmic-praise)$ pip uninstall python-rtmidi
  2. Download the python-rtmidi source from
  3. Edit and change the line that reads libraries += ["pthread"] to libraries += ["pthread", "stdc++"]
  4. Run pypy install and try running the client again.


Cosmic Praise 52' tower lighting & associated electronics


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