Sep 12

Construction of a new 3D projection dome at CMU

Scientific data visualization is an important aspect of science in general, and materials science in particular.  Our field is highly visually oriented, since we focus most of our research on microstructures, which we then need to image one way or another.  With the increased emphasis on 3-D data sets (as well as 4D data in our present MURI program), we realized early on that there would be a need for a dedicated system to visualize such data sets in 3D. After exploring the various possibilities, we settled on the so-called iDome, a 3D hemispherical projection dome.  You can find many examples of such domes here.  After visiting Matthew Dougherty at Baylor College of Medicine in Houston in January, to take a look at his dome setup, we decided to build a hemispherical dome with an 8 ft inner diameter, with a mounting frame that would allow the dome to be tilted in the 30° to 70° range.  This required the design of a mounting frame (as well as finding an empty corner in a lab to place the whole contraption). 


As we are in the middle of dome construction, we will post updates and photos of the project on this page. The early drawings were just pencil sketches on paper, starting around the middle of March, 2014. An example of such a drawing is shown on the left above; this is a sketch of a metal flange designed to hold the fiberglass dome so that it can be tilted around an axis. A more formal (Google SketchUp) drawing is shown in the middle; this was used to figure out the 3D mounting of the dome, using metal construction components from the 80/20 company. On the right is another conceptual drawing, showing the relative positions of the dome, the stereo projector, a spherical mirror, and the user.

After obtaining permission from AFOSR to reallocate a small portion of MURI funds, we started the acquisition of project components.  The fiberglass dome was ordered from Architectural Fiberglass, Inc. in Cleveland, OH, and delivered in eight octants in late June.  The spherical mirror was ordered from Go-Dome in Houston, TX; it arrived early June.  The frame components arrived early June as well, and were assembled by the end of June, after the lab corner was fully vacated and prepped (new floor tiles).  Three work study students (Drew Schwab, Daniel Wolf, and Pieter De Graef) painted the outside of the dome octants black, and bolted them all together into a single dome, which then sat on the floor of the lab for a while. 


In late July, the mounting flanges were ready (fabricated by Adam Wise and Larry Hayhurst of the Chemical Engineering machine shop) and a crew of nine people (below left) hoisted the 450 lbs dome onto the mounting frame (right).


In early September, Jason Wolf, Adam Wise, and Marc De Graef covered the front of the dome in plastic sheeting (below left) to start the process of prepping the dome surface for the application of the screen paint.  First, the seams between the fiberglass octants were filled with fiberglass strips and resin, followed, after curing and light sanding, by a thick layer of Bondo to completely hide the seams.  After sanding (and producing a whole lot of dust inside the sheeted area), the surfaces were cleaned, a base coat of paint was applied, followed by an application of Screen Goo (2 reflective coats, 2 finish coats).  Then the dome was allowed to sit for a while to fully cure the reflective surface.  Meanwhile, a Sony VPL-HW40ES stereo projector was acquired, and a mounting frame was built to support it as well as the spherical mirror.  The projector was tested to make sure that it properly responds to a frame packing s3d HDMI signal, since not all 3D projectors will automatically switch to this mode; turns out that it does without any problems, so we're in (3D) business.  Below center and right show the inner part of the dome after all Bondo layers were applied.  Next stage is spray painting, which was completed on Sunday October 12, 2014.


Finally, after a lot of work, the projection dome is ready! A strip of color LEDs was added to the edge of the dome to provide some interesting lighting effects when the dome is not in use (rightmost image below). The image on the left shows the projector, and the one in the middle shows the temporary mirror mount.  The geometry of the whole system was calibrated with significant help from Matthew Dougherty (Baylor College of Medicine) during the week of October 13, 2014.  The dome is now fully operational!