Jul 06 2009

OpenSim Terrain notes, and Darb has Process Credit history!

I’d read about this, but never before experienced the agony first-hand.  Extracting funds from SL, the wait for funds to arrive at PayPal was a bit slow.  In fact, in the time it took funds to go from Linden to PayPal, a bamboo shoot in my back yard could have grown taller than me (that’s my RL not SL height!), and would have been over 2 meters tall.  Anyway, Process Credits are quite lacking in symmetry with how quickly credit charges can flow into the Linden realm.

During this week of waiting my random prims have been cleared out from Amida and nary a trace of Berkurodam BART Station remains besides a video in Gualala.  The video screen was actually entombed by a neighbor, who may not like it but did not send any message.

Anyway–for me this week is all about generating maps and graphics while keeping up with work.  I’ve generated a 50cm terrain grid for parts of my county where perhaps 150,000 people live.  With computational process improvements I should be able to make production stable enough to generate a 25cm grid.  The point is to model terrain slope and aspect within urban parcels.  OpenSim can pack 64 terrain megaprim sculpties over each region to refine terrain more than the built-in 1-meter postings, and display 10cm orthoimagery at full resolution.

Last year, I used first-return LiDAR data of the UC Berkeley campus to generate a 25cm grid for 10cm imagery.  Now, I’m working with bare-earth LiDAR data from FEMA, topographic contours (densified to 1.5m vertex spacing), and most importantly, photogrammetric terrain and water break lines.

Throwing all those data into the mix, the data are built into an ESRI Terrain Dataset, from which I generate TIN and GRID models at various reolution and extent.  The ESRI ArcGIS 3D Analyst Terrain-to-TIN generator breaks down after about 10 mega-faces (so would I…)  And the ArcGIS Terrain-to-GRID generator seems to drift into Windows-unconsciousness after about 1.0 giga-cells.  So for the grid, I break it down and do the pieces, then merge the tiles using ERDAS Imagine, because the ESRI ArcGIS raster mosaic function does not produce output grids much over 10 GB.  As annoying as learning these ArcGIS limits can be, it is very satisfying (and instructive) to see huge swaths of seamless terrain with great detail once it all comes together.  Thanks to the break lines, many driveways and most home building site cuts and fills are resolved.  And it will be a lot of terrain by OpenSim standards–enough to calibrate terrain for over 20,000 contiguous regions–not that I ever expect to build it all at 1:1 scale!

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