Thursday, May 10, 2012

Playing in a virtual sandbox

When I was a little lad, there was nothing I enjoyed more than playing in a sandbox in the back yard of my parents' house during the summer. That old sandbox became a place where I could construct my own virtual worlds filled with castles, mountains, river and oceans. It was, as I recall, jolly good fun.

But in this age when computers dominate most every aspect of our lives, it should come as no surprise that even the humble sandbox has now been transformed into a digital experience.

That’s right. As part of an NSF-funded project on freshwater lake and watershed science, the good folks at UC Davis (Davis, CA, USA) have created a sandbox that allows users to create topographic models by shaping real sand which is augmented in real time by an elevation color map, topographic contour lines, and simulated water!

While it sounds like great fun for kids of all ages, the sandbox hardware built by project specialist Peter Gold of the UC Davis Department of Geology has actually been developed to teach geographic, geologic, and hydrologic concepts such as how to read a topography map, the meaning of contour lines, watersheds, catchment areas, and levees.

To do just that, the system makes use of the Microsoft Kinect camera which continuously collects images from the sandbox as the user interacts with the sand. The 30 FPS images from the camera are fed into a statistical evaluation filter which filters out moving objects such as hands or tools, reducing the noise inherent in the Kinect's depth data stream, and filling in missing data.

After some software processing, the resulting topographic surface is then rendered by the projector suspended above the sandbox, with the effect that the projected topography exactly matches the topography of the real sand. The software uses a combination of several OpenGL shaders to color the surface by elevation using customizable color maps and to add the real-time topographic contour lines.

At the same time, a water flow simulation is run in the background using another set of GLSL shaders. The simulation is run such that the water flows exactly at real speed assuming a 1:100 scale factor, unless turbulence in the flow forces too many integration steps for the driving graphics card to handle.

The researcher say that the software they developed to create the virtual sandbox is based on the Vrui VR development toolkit and the Kinect 3D video processing framework. For those wishing to develop their own sandbox, they say that the software will soon be available for download under the GNU General Public License.

That's surely good news for all those of us who would love to take a trip back to our childhood by sampling the new virtual delights of the sandbox in our own living rooms.

More information on the augmented reality sandbox can be found here.

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