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Thursday, November 11, 2010

DBG Project Feedback System

One of the visual highlights of the Botanical Gardens gig was the use of video feedback for a large section of the dance piece. However, unlike most feedback systems, ours had to have a slower flow than you can typically get, and had to be able to self-stimulate when a dancer entered the visual area.

The system we came up with - which we dubbed "pixel glide" - was a combination of a few techniques that turned out to give good (if still somewhat uncontrollable) results. A camera fed the current image into a Jitter-based patch that provided some brightness, contrast and saturation adjustments (which I could perform from the central computer). From there, it went into a jit.slide object to slow things down a bit. The result was mixed (at about 75% to 25%) with a highly contrasted image of the sculpture's rough surface. This was then sent to the projector to complete the loop (since the camera was pointed at the projection surface).

The sculpture-texture was dark enough that the areas unoccupied by dancers offered little in the way of feedback action - the jit.slide and the low-light saw to that. However, when a dancer entered the area and was illuminated by some of the highlights of the texture, the system would kick into speed and begin flaming, roiling and twisting. Some of the activity was based on the location of the camera (on a platform about 4' high, mounted on a tripod so it was about 8' in the air), the offset of that location from the projection location, and any zoom and panning that we did. Some of the panels flamed straight up, others twisted in an arc and others created filmstrip-like image feedback along the length of the projection area.

It was a highlight, and people seems to love it. I'm sure I'll be using this one a lot more...


Tuesday, November 9, 2010

DBG Project Network Topology

Above is a basic overview of the layout for the DBG/Moore performance. The projection system featured 9 projectors (four for the walls, four for the illuminated cubes, one for the main scene background), driven by 9 computers (4 G5's, 4 Intel Mac Minis and 1 Intel Laptop). A tenth computer, my personal laptop, was the central driver.

Basically, this central control computer sent OSC messages to the other 9 computers which forced them to conform to scene changes. The videos were not hard sync'd, so there was no need to have a timing source. However, the central computer did send out "ping" messages, since otherwise we were finding that the network interfaces would fall asleep on the G5's and would stop responding after a while.

We created our own network using a Netgear router not connected to anything. My only mistake: we named the network "DBGONLY", which apparently was too interesting for some hacker-types to withstand. All afternoon I was fighting with people hopping on the network and dumping my systems off. I finally locked down the network and everything was fine.

It felt pretty cool to sit along the side of the room and control this whole system from behind a podium. Felt like God - or at least like the Wizard of Oz.