Just as they enter, visitors to Boston’s Museum of Science get a unique kind of chemistry demonstration, played out on a wall of 24 high-resolution screens depicting swirls, waves and irregular speckled shapes.
The Reaction-Diffusion Media Wall displays a 13-foot high simulation of chemicals that react, mix and morph to create elaborate new designs. The exhibit is interactive, so visitors can create their own designs.
The GPU-powered simulation shows museum visitors how two virtual chemicals, shown as white and dark blue, can continuously react and diffuse to create biological-looking shapes.
Karl Sims, digital media artist and computer graphics research scientist, developed the simulation. “I was interested in finding a fun demonstration of emergent behavior where simple rules can be repeated to create complex results,” he says.
The simulated chemical reaction is the process of one substance replicating when it finds and consumes the other substance. As this happens, the chemicals diffuse to spread across the grid. In this display, the white chemical spreads faster than the blue. The different rates of diffusion, along with the reaction, lead to complex behaviors in forming patterns.
Sims explains that he chose the model of two chemicals reacting and diffusing because “it produces such a wide variety of natural-looking, dynamic patterns when just a few variables are adjusted.”
Museum visitors adjust these variables, with the help of a touchscreen kiosk in front of the display. They can press several predetermined patterns resembling a fingerprint, tree rings, brain coral or cheetah spots, and then watch the parameters slide to new positions on the screen as the selected pattern grows on the video wall.
Visitors can also generate different designs by adjusting the “feed” and “kill” rates, which control the speeds of white chemical production and blue chemical decay rate in the simulation.
The Reaction-Diffusion Media Wall runs on a Linux workstation powered by an NVIDIA GeForce GTX 980 GPU. “The same processing power that provides gaming performance can also give fast general-purpose calculation,” says Sims.
The GTX 980 worked well in helping Sims develop the simulation, but he did come across one surprise. “After I’d optimized the code to take full advantage of the GPU, some parameter combinations were giving results that were actually moving too quickly for visitors,” he explains.
To solve this, Sims added a predefined “speed map” that can automatically speed up or slow down the simulation so different parameter combinations wouldn’t create dizzying motions.
Whatever variable they decide to change, museum visitors will experience what it’s like to transform chemical compositions and watch new patterns form every time.