Apr 18 2008

OpenSim svn 0.5.4_4272 Supporting 40 regions

Published by under OpenSim,SL In General

I’ve been in a bit of a rut the past couple of days, feeling doubt about which way to proceed with configuring the OpenSim side of the UC Berkeley campus 1.024:1 sim. For the first time since I started setting up OpenSim test servers back in October 2007, I was uncertain of my ability to make it work with this project. I rolled back to 0.4, 0.5.0, 0.5.1, and the trunk that worked a couple of days ago would run only 32 regions well, and even at that would stop working, without any use, by morning. All my effort was going into testing out various ways of retreating from the leading edge. In an activity like OpenSim, that’s not a fun place to toil!  Now, after the sim sits quietly through the night, I can teleport from my landing zone in the far SWly region to the far NEly region, and get there pronto.  Plus the 40 Regions are barely consuming 1% of the CPUs.

Realizing that a good 48 hours had passed, one of the things I tried tonight was a fresh grab of the trunk, and that really turned things around for me. With OpenSim 0.5.4_4272 I have the same rocket-fast launch, zippy association of terrain with regions, and I can actually teleport into regions that haven’t resolved their terrain without finding my av hung up. That was all good. Then, I started moving around the ERDAS Imagine data that will be stamped into terrain megaprims, and I was reminded that I’d gone to all the trouble of resampling both terrain and orthoimage for 40 regions, and my diced file naming conventions were already dependent on that entire set of 5 x 8 regions. So rather than fire up the process for making sculptie bump-maps, I went back to the 0.5.4_4272 build, shut it down and went after my region configuration–willing to give it another try at 40 regions. While I was at it I generalized my PHP region XML configurator.

Just for the sake of enjoyment, here are a few views, including nice Windlight night shots. Compared to two days ago, one can notice more of the hill at LBNL, with the fairly intricate grading for service roads and laboratory buildings quite evident in the scene.

40-region UC Berkeley OpenSim 40-region OpenSim at UC Berkeley 40-region OpenSim of UC Berkeley at 1.024 : 1


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Apr 11 2008

OpenBerkurodam and the well-tempered scale

Published by under BART Station,OpenSim,Scale Issues

Enough carefree hours in the main SL Agni grid, already! Back to matters of creation.

Next big thing should be a terrain prototype for civic application. No special business process in mind here, just a demo of the draped imagery on real-life terrain in a way that could scale up city-wide. For starters, there must be a better correspondence between the US National Grid and the dimensions of the simulated region. Sure Neal Stephenson may have suggested binary 2^n dimensionality, and there may be plenty of reasons in the simulator code to make use of the full range of 256 meters. But after more than a handful of regions, the starting corners get downright ugly.

So I won’t do it that way. By scaling up, larger even than real-life, the regions can be built sixteen-to-a square kilometer. In a worldwide sense, except for the matter of 62 or 64 matchlines, the US National Grid (a.k.a. Military Grid Reference System or MGRS) has the whole world in its hands, so harmonizing region design with that grid plan covers a whole lot of ground. To minimize my effort at constructing regions, while planning for worldwide sim grid extensibility, I have chosen to configure the overall sim to represent 250-meter square patches of real earth using each of its 256-meter square regions.

This scales the real-world up a shade in the sim, to (1.024 : 1) but allows every fourth region in X and in Y to start on an exact grid kilometer. That scale produces 16.0000 regions per square kilometer, rather than 15.2588 regions/square km. From the geography side of things, this harmony is attractive since every fourth region will snap to a grid kilometer instead of every 1000th region. Even at that, the grid kilometer that 1000 of those 256 meter regions snap to is 256 kilometers, which is much clumsier to locate by name.

Thus the “well-tempered” moniker for this scale is well deserved, as any real-world USNG/MGRS grid coordinate could then be used to search for the relevant simulator region from a moderately simple bit of string manipulation. For Berkeley, and the western part of California, the zone is “10S” and the 100-kilometer grid within that is “EG” for San Francisco and Berkeley area. Put together, the US National Grid designator for the 100-km square is sometimes called “10SEG”, depending on where folks do or don’t put spaces.

If we always have exactly sixteen (16) regions per square kilometer, then we can use the shorthand version of the USNG grid names that only detail down to 10-meter increments. In this way, a region with its southwesterly corner at WGS84 UTM zone 10 north, 564000 meters Easting, 4191250 meters Northing, can have the US National Grid 10-meter designation of “10SEG 6400 9125”, which could be mashed together without spaces, or used to name a simulator region such as “10SEG_6400_9125” in a slightly more readable form. For those of us who no longer have youthful eyes, the tiny little display on the Second Life client for the region name motivates the use of spaces.

So here’s a graphic of the plan: a 40-region prototype (5 x 8 regions), which will be configured with only Basic Physics, but real-life LiDAR-based terrain, and four megaprim sculpties per region to drape imagery (10 x 16 terrain sculpties) such as 10cm natural color orthophotography. Here’s where I hope to take this:

Charter Design: US National Grid standardized OpenSim regions for Berkeley Downtown / Main UC Campus

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