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Reflections On Feedback

ADE / Soundlab

‘Reflections on Feedback’ consists out of a laser, over 150 mirrors, a multi-speaker surround setup and a software system that is based on feedback for sound-synthesis and management of sound and visuals. For ADE Sound Lab Naivi developed new software whereby mirror reflections are translated into sound and where light and sound affect each other.

The pieces that hold the individual mirrors are 3D printed, the frame that surrounds each individual segment is manufactured out of high quality aluminium. To create a 'floating feel' the installation supports itself using only stainless steel cable. The entire installation has been designed, calibrated and simulated in a 3D application before being manufactured and assembled, saving us a lot of time and energy. This gave us the confidence that the physical installation would match it's digital counterpart.

For this installation we created a custom application. Both the multi channel audio and generative visual part of the application work from within the same process: allowing the audio to influence the laser and the other way round. This creates a controlled feedback loop that in turn creates intricate, ever expanding patterns. The app pre-visualizes all the generated shapes that are send to the laser using a canvas that shows an individual render target for every running laser instance.

To achieve a very smooth laser experience (no flickering) the application resamples all the lines based on the individual laser requirements. This means that a steady 60hz laser output is guaranteed. We wrote our own C++ interface to the Etherdream Laser DAC that works on Windows, Linux and OSX. This allowed us to circumvent costly propietary laser solutions. The laser IO is handled on a seperate thread to free the main thread from having to wait for the laser to finish. The main application renders as many frames as it can, averaging around 500+ fps on a medium spec desktop machine.

To deform the laser lines we created a modular mesh processing pipeline that modifies the lines in a sequence of steps. The output is uploaded to the GPU and send to the laser. Because the entire processing pipeline is in 3D the laser receives 3D shapes that are reprojected using a laser projection matrix. This allows for interesting effects in the physical space where a laser light source can rotate around and collapse in on itself.

Rendering is done with our own renderer. The audio is generated using our own multi channel audio engine. Etherdream dacs were used to convert bits to laser acceptable levels of voltage (ILDA). The entire app is written in C++ using our own NAP creative coding framework.

During ADE people admired the installation for extended periods of time, something of a rarity nowadays. Visitors tols us they experienced it to be both hypnotizing and evocative, sometimes even emotional. The installation was well received and deserves to shine again.

We'd like to thank Neil Chatterjee for designing and building the actual installation and Stijn van Beek for writing and hooking up the generative audio part of the application.