Something regarding PD

---------- Forwarded message ---------- From: Bennett Smith bennett.smith@music.mcgill.ca Date: 2011/5/18 Subject: [Mumt_grad] Fwd: PD To: mumt_grad@music.mcgill.ca

Here's an opportunity for some interesting work:

Begin forwarded message:

*From: *Jordan Deitcher jordan@liminal.ca *Date: *May 10, 2011 10:39:59 AM EDT *To: *Bennett Smith bennett.smith@music.mcgill.ca *Cc: *Mitchel Benovoy mitchel.b@gmail.com *Subject: **PD*

Hi Bennett,

We're looking for somebody to do the following. We were hoping that the guy who did our particle system would do this, but he can't right now. Here's what Mitchel wrote to him. Zack and Mike thought you might know someone who could do this. Would you be oh so very kind and let me know? Thanks.

Jordan

Hi Reuben, After consulting with a PD expert, we're going to change your workplan slightly. Basically, you will not need to port your C++ code into PD Externals, as this might result in suboptimal CPU scheduling. Instead, you should use PD purely as an interface to control the particle system, which will be running in a different thread. The communication between the particle system and the PD interface should be done using Open Sound Control (OSC), which is an efficient UDP communication protocol. The idea is use OSC to send commands to the particle system (like changes in the parameters). This is fairly easy to do: you need to implement an OSC handler in your code that listens to incoming messages from the PD interface that you will design.

I suggest you familiarize yourself with OSC before you get started on this ( http://opensoundcontrol.org/introduction-osc).

Here is what our PD expert had to say:

=== So my suggestion for the particle system / Pd thing is: Don't make a pd external that contains an OpenGL rendering loop. It's suboptimal because you'll need a non-blocking polling and/or drawing mechanism. Pd expects to be in control of scheduling. If you draw GL in the same thread, you'll get blockage of DSP (clicky audio). If you draw GL in a separate thread, you'll need mutexes or condition variables to tell Pd when it's allowed to change the GL content (ie, between frames). This is tricky scheduling, and not necessary for what you're doing.

A better solution is to provide an control interface via OpenSoundControl (OSC). ie, the particle system would be in a separate process with a socket that listens to control messages. You do a non-blocking poll of your sockets between frames. There are lots of libraries (eg, liblo or oscpack) that you can use for this.

On the Pd side, I'd highly recommend using my [OSCrxtx] objects for sending messages:http://code.sat.qc.ca/pdsheefa/trunk/src/OSCrxtx/

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