Kiwi PyCon 2011, Wellington, Spotlight on Python by Nick Cave-Lynch, Spotlight on Python. Covers development and use of a Python-powered system designed for lighting bands in small venues. Covers (among other things): the problems of lighting bands; the development process; the results; lessons learned.

1. Spotlight on. Python
Python for realtime control
of stage lighting
Nic Cave-Lynch – Tymar Lighting

2. Spotlight on. Python

The problem

Current architecture

Version 2 architecture

DMX Engine

RDDD (Rubber Duck Driven Development)

Observations

3. The problem

Lighting bands, typically in small-ish venues

DMX: 40 updates/second, 200-500 channels

Moving lights (HTP/LTP)

Music usually new to me

4. 'Busking' in 4 dimensions

5. Enhance the music

6. Enhance the show

7. Current architecture
Input wing: serial asynchat DMX engine asynchat USB DMX
faders gathers HTP/LTP -> sends
generator
buttons wing input channel value DMX
USB (fcntl)
moving light Mimic
trackball capture
manager (wxPython)
trackball

8. Version 2 architecture
USB/ USB/
Input wing: serial/
ZeroMQ ZeroMQ DMX serial/
faders MIDI Input wing DMX Wifi DMX
generator
buttons controller struct engine struct generator
controller
trackballs
ZeroMQ ZeroMQ
protocol protocol
buffers buffers
Config UI / mimic

9. DMX Engine
 Engine()
– Holders for Valgens, Scenelets, Fixtures
– dispatches zmq messages from wing/UI
 Valgens know which Scenelets they drive
 Scenelet sends multiple of Valgen value to Fixture channels
 Fixture has channel for each aspect of the light
– output function eg calculate pan/tilt values from (x,y,z)
 Speed important:
– reduce lookups
– integer dict keys
– Valgen->Scenelet->Fixture single function call
– struct module

10. RDDD

Architecture took ages

Rubber Duck Driven Development

"make something that doesn't work"

11. Observations

Unit tests inhibit experimentation

Deciding to Open Source can be an inhibitor

Spoilt for choice in libraries/frameworks/etc.

Analysis paralysis

Surprising results in some performance areas

struct module

string/integer dict keys

I hate OpenOffice.org Impress 3.2: it's barely useable

12. For more live Python action
200 metres from dinner venue:
● Left out of Tulsi
● 20 metres to Guznee St
● Right up Ghuznee St
● One block up
● Straight over traffic lights
● Bodega is on the left