Darb Dabney’s OpenSim Blog

With some preliminary surface features in place now, there are textures on the station cupola and easterly face of 2150 SHATTUCK AVE. I used my venerable Canon A-1 with Canon FD 14mm f2.8 L rectilinear wide angle lens to capture some textures. After getting things pretty well squared up with the powerful analog optics, I made a 35mm shot, had it processed at Long’s Drugs where one can now get 35mm film processed directly to CD for $2.99/roll with C-41 processing and an index print. If one asks for the “5×7″ scan resolution, there is a 1535 x 2137 (3.1 Mpel) scan for every full frame which throws out a fair bit of detail but seems adequate for most 512 x 512 textures in SL.

I tried fairly hard to get the subject building face filling as much of my field-of-view as possible, knowing that the CD scan will be less than I’d try to squeeze off from a 4×6 (10cm x 15 cm) glossy print in my own scanner.

Despite my best efforts in the viewfinder, things always seem a bit warped in the scan when I first view them on the screen. For that, I bring out the big guns. Using Adobe Illustrator I make a sketch of any repeating geometry that is in the building (say 11 floors and 16 windows per floor), render that as a TIFF and use that for registration in ERDAS Imagine. With a second-order polynomial warp, perhaps 16 well-distributed control points, I can get the texture close enough to impress on first blush.

When grinding through the control points, one’s mind may wander. In my case, I considered the terminology of how ERDAS ground control points (GCP) as might help georeference an image are being used in this task as texture control points (TCP). There is no projection per se, but there certainly is a load of rectification going on. With ERDAS, it goes on about as well as one has the patience to give it.

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