Darb Dabney’s OpenSim Blog

With many thanks to the globe-spanning OpenSim community, I have seen the error of my sourcing ways and replaced a version of Open Dynamics Engine that I had compiled on my Ubuntu x86_64 system, on 20080220, leaving the product of that effort, libode.so, up at /usr/local/lib which seemed well and good at the time. As things have evolved, ODE was brought into opensim-libs svn at some point after the last change log entry at 20080328. I was happy to find that ODE was included in the OpenSim svn, and turned on the physics engine in my OpenSim.ini configuration file.

Where I went wrong was not clearing out the library I’d compiled back in February, because that directory was getting sourced before my latest version in each of the nine OpenSim svn builds I’ve made since April. Last night, Dahlia helped me get focused on fixing the problem that I was having and she demonstrably was not. Teravus cleared up that my issue was squarely that of ODE and nothing but ODE, and Nebadon pointed me to exactly the updated documentation that I needed to build my own new ODE for the first time since I’d migrated the test server to Ubuntu 8.04 from 7.10.

In the process, I’ve learned to expect more efficient memory usage than I’d been understaning. I had written to Nebadon that my 40 regions were using 1.4 GB of memory, but once I had to start killing processes after every sphere I’d rez, I saw that the processes that I was killing were all less than 900 MB memory. And now, with ODE, MySQL region and asset storage, and 40 regions, I get OpenSim console statistics showing 194 MB “Allocated to OpenSim”.

Here is a video of what the old ODE (20080220) did with a really big cube (25-meter sides dropped from 500 meters)

After compiling ODE from the OpenSim-libs/unmanaged trunk, and adding a few build tools to my server, I got a fresh libode.so that was 3.7 MB rather than the 3.1 MB that was distributed with svn 5234. I did not tweak any compile flags as this was from OpenSim folks’ favored setup. After ODE was working, I slept well and awoke very optimistic about my prospects for getting a demonstration public-facing by end of July. I also have enjoyed testing the performance of ODE, particularly after Dahlia shared some time on her Dev server at OSGrid.org.

With ODE running, certain physical prim movements can consume plenty of CPU cycles, and even with two avs and some complex mesh interactions, there can be striking lag. So with my own regions working once again, I wanted to see how that looked, and I was inspired by the 1967 TV series The Prisoner to create an oblate spheroid (5 m by 5 m by 4 m) as a physical prim to roll after Ruth. The first of my efforts was shot here, and as you can see, I used Rover’s Dutch cousin, as orange was much easier to see than the original Welsh white Rover.

Finally, to impart a sense of drama, I textured Rover with a menacing City of Berkeley sewer manhole cover, and finished the celebration of ODE with a long take including several region crossings and a pleasant sunset hue from Windlight. As I hope is clear with this video, OpenSim has really come a long way in the past couple of months!

I’ve been trying to be patient and catch a good wave in OpenSim’s evolution, so that I can configure a demo of terrain prims for late July. Much good seems to be afoot, and yet I am trying to find the right point amidst all this progress to grab an SVN and build on it for a few weeks. Tonight I had some luck with getting my OpenSim.ini configuration together better than before.

For all OpenSim back end storage now I’ve gotten MySQL 5.0.51a-3ubuntu5.1 working fine. I had a glitch in my configurations where I worked with a configuration setting that referred to Catalog / schema (what MS SQL folks might know only as a “database”) but interpreted as schema certain tables within that one schema known as users, userfriends, terrain, prims, land and such. For a few nights I seemed sleepily unaware that I had confused the table ‘opensim’ with the catalog ‘opensim’—my bad for naming them all the same without being sure enough what I was doing. The symptom was simply that
../cli OpenSim.exe
refused to load storage, which is to say that the sim wouldn’t start up, and refused to go more than the first few lines into a startup sequence that for my 40 regions is typically many hundreds of status lines. Anyhow, that’s all happy now and every storage invocation in my OpenSim.ini config is using the local MySQL instance through loopback. Bottom line for me was this—the OpenSim.ini and mysql_connection.ini config files are connecting to a catalog, even through in places they contain references to certain tables.

On the physics side, I’ve got ODE turned on for all 40 regions, and the startup is still very fast at less than 30 seconds with no prims. The 1-meter gridded terrain loads into 40 regions in about 15 seconds [hardware: 2x Core2 Duo E6550 overclocked to 3.4 GHz with 3.9 GB RAM]. Everything seems to be going my way until…

I try to create prims right now. Tonight at svn 5195, I can create cube prims, have them be physical and drop to the ground. When either I turn them into spheres, or create them as spheres, in regions near (where I first rez) or far (at the northeast end of my 40 region sim), the whole sim hangs brutally. I’ve never had the sim hang this way before, where it’s a ‘kill -9′ to get its attention and make it go away.

With the persistence of MySQL running, if I quickly restart the sim without taking time to command the previous “../cli OpenSim.exe” into oblivion, then I can’t log in because the second sim still thinks that I’m already logged in, from the first hung sim’s session. I flailed around a bit this evening learning this and creating new users along the way. At one point, I was so discombobulated between hung mono and typing anything *.exe on a command line that I restarted Ubuntu to wash my hands of the matter. Now wasn’t that silly? I certainly think that it was. No amount of C# code under mono is going to turn Ubuntu into the sort of bounce first, ask questions later mode favored by some Windows server administrators, including myself in impatient moments.

But whatever happens tonight at svn 5195, it appears to have an evil effect on mono when meshing a single spherical prim, or a box that’s become a sphere. This is using SL Windows client 1.19.1.4 or SL Linux client 1.19.1.4 on x86_64 Ubuntu 8.04 Hardy Heron.

Thanks to Nebadon who helped me get a pulse on my memory usage. Interesting experience tonight was that now that I’ve started using MySQL and making sure to kill off zombie ../cli processes, my memory use is down toward 780 MB, rather than the 1.4 GB I’d mentioned on IRC. At that size, there does not seem to be too much memory use penalty under Linux+mono versus native Windows servers running OpenSim. Selfishly, I’m glad of that because I’ve already switched my opensim test servers off of Windows and onto Ubuntu, and I’d prefer not to come across too many reasons to want to go back!

After mucking around a bit, I was able to use free tools to browse the contents of the classified LiDAR, then used ArcGIS 9.2 tools from 3D Analyst and ERDAS Imagine to get where I wanted to go with this surface. First, I needed to know how many returns there were, and what each of the classes meant. The LAStools info function helped there. Then I used ArcGIS 9.2 3D Analyst “LAS to multipoint” conversion tool, but selected only the first return. Multipoint was an annoying format because it did not seem to fit anywhere in the cool new ESRI “terrain” feature data type. In the end, I gave up on ESRI terrain and went straight to the classic TIN. For maximum overlap, I did not filter out any specific angle from nadir, taking whatever was sent along from the contractor to Alameda County.

Of course, I had to negotiate the treacherous 3D Analyst menu items that were necessary. Getting multipoint into a TIN required creation of a TIN (obvious, but with blank result) and then the non-obvious choice of “Edit TIN” which effectively accepted the multipoint data that were imported from LAS and allowed me to specify the delunay method of choice. Once canned as a TIN, it was a familiar step to specify a raster gridding. I haven’t found a way to reproject the TIN, so I was still in NAD83 California coordinate US Survey feet, and an assumed NAVD88-Geoid 2003 CONTUS-feet vertical while I tried several grid resolutions. In the end, I was happy with 1 foot gridding.

Then, raster on disk, I was able to reproject to WGS84 UTM zone 10 north meters, and chose bilinear resampling on a 25 cm grid posting interval. Once in my favored projection, I rescaled the Z values to NAVD88-Geoid 2003 CONTUS-meters, and began to examine the need for a bit of grayscale morphological processing. I’ve been a great fan of mathematical morphology for over 20 years, so it was a pleasure to craft a kernel or 3 to compensate for some artifacts. Because the TIN-to-grid was so highly oversampled, I was able to use a combination of a tall, narrow 7×3 kernel for morphological CLOSE, followed by a 3×3 DILATE, and a diamond-shaped 5×5 ERODE to finish off the task. In case this morphological stuff sounds like odd stuff to do, these operators are variations on focal max and focal min convolutions. The results are rather important for my application, as shown in the following images.

First is the reflective DEM surface, and the same with the Open Berkurodam 40-region overlay.

Next are more detailed images, near the Greek Theater, showing why I ran the morphological filtering and also how I was able to mostly conserve building footprint areas while inflating trees. The main artifact attenuated was interlace-type effects at the end of overlapping LiDAR scans. The long axis of the morphologcial CLOSE kernel was perpendicular to these artifacts.

Here is the morpho-filtered reflective DEM, with the 10 cm natural color imagery overlaid.

Next up, I’ll need to figure out how to best use this 25 cm surface. It really seems a shame to use it in the way that I have thus far with terrain megaprims–where using four megaprims per region I have effectively downsampled the terrain to 4.26-meter grid postings. That wasn’t so bad for the bare earth model. Here I’ve got something over 290 times denser with 0.25-meter grid surface samples.

But to use many more than 160 megaprims for the entire 40-region model, I really must automate the placement of the (auto-generated) sculpties. For that, I’ll need to ask around the OpenSim community for advice!

The classified LiDAR data that I hope will provide some inflated structure and tree surfaces for draping the orthophoto have been reviewed. I find the data beautifully detailed, and fascinating to see with GeoCUE Point View LE. I’m working with the UC Berkeley Geospatial Imaging and Informatics Facility UCB GIIF, also known as the Maggi “Kelly Lab” when proximal to Mulford Hall.

Right now my goal is to interpolate the first return surface in a way that I can grid and filter most appropriately to inflate buildings and trees. In principle, I should be able to use the first return LiDAR point cloud to create a NURB surface that would be expressible as an OpenSim/SL sculptie. But I’m going to take a more cautious approach and try to get the whole thing gridded in a consistent way so that I can reasonably expect to cover the entire 40-region sim with good inflated surfaces rather than the bare earth that has been a fine demonstration, but a bit flat for draping the orthophoto.

I’m going to throw out a lot of images and let them speak somewhat for how the classified (into ground, structure, low veg, med. veg, tall veg) LiDAR point clouds look.

Here’s the plain elevation image and the classified view of same

this is how the classified image looks with intensity shading. It gives a first impression like a photo

Some perspective views also help to show what information will be available for gridding. For these I’ve displayed with vertical exaggeration of 1.5X

This experience was on 3 June but I’m only writing about it now. Much the same as on Monday where the regions start up like gangbusters, terrain loads in a snap, and everything is navigable with no prims. When I get myself to the most interesting terrain, at UCB’s Greek Theater, I rez a cube and it sits on the ground. When I carelessly resize it to 10 meters in all dimensions, part of it sits below ground. After all, it is not physical yet. Then when I set it to be physical, either as a cube or after making it a sphere, the whole sim crashes. Looking at Mantis I had the sense that some aspects of this issue have been worked on very recently and resolved. So far for me, no joy.

I also have a challenge with getting region and asset storage working on MySQL rather than SQLite. People need persistence for any difficult build, and when things get large that’s not the time one wants to run up against the limits of the storage technology. But I’m flummoxed by the necessary OpenSim.ini config. I’ve seen this work on other sims at earlier revisions, so I know that I’m close. But I can’t get OpenSim to connect, although I have no problem getting to the catalog with MySQL-administrator and I do see some tables get created if I leave SQLite for region storage and MySQL for asset. But when I try to use MySQL with all storage, OpenSim complains that it can’t find a responsive instance of MySQL. Suspicions are pointing toward my mixed use of localhost loopback 127.0.0.1 and local network address 10.x.x.x among OpenSim and MySQL installs. Even though I run standalone, I need OpenSim to respond to the local network address to access OpenSim from other machines in the lab, and I thought that I had MySQL set up to do the same. Apparently some connections must use loopback and that may be creating inconsistencies that keep me from launching OpenSim in a non-SQLite setup

For the Linux SL client on my HP keyboard, (Alt- + Windows- = Alt- ) as the SL client works in Windows.

Yesterday evening I added a YouTube embed to a post, and it showed up today with a toxic URL in it. That edit was made from Windows, so tonight I’m running Ad-Aware full scan, which takes awhile. So to keep at it, I took the test server (E6550-3.4 GHz/4GB) and ran it with 40 regions standalone, real UC Berkeley terrain, and ODE; then to be testing I installed the latest now-Beta SL client 1_19_1_4 and went for it!

Things are getting ever smoother with the Second Life client for Linux. I first fired it up and went to Agni, and saw that the 1:25 scale Berkurodam model rezzed much more slowly than it did when I last tried the Windows client a couple of nights ago. I say that because I saw the ellipsoids of the sculpties, as ellipsoids, for many seconds.

Then I quit and launched with “./secondlife -loginuri host:9000″ and saw the terrain rezzing like never before. One of the wild things about OpenSim is that if you try something that you’ve done before eons ago, like three weeks, things can be different in some really good and unexpected ways. Like the speed with with terrain rezzed once I set my draw distance out to 512 meters and flew to a NEly corner of a sim. Wow, I’ve never seen so many regions filling in at once, and nary a delay for the little texture patches that follow along. It made me think that network speed limits some of the experience, even when its a local 100-Mb wire.

Anyway, I was able to saunter in flight all about the 40 regions and be fairly impressed. Then I stopped by the Greek theater site, rezzed a 10-meter cube and threw it up 1 kilometer into the air. It landed with much less bounce than I saw on the default sinc-shaped islands last night, but still looked as slippery as an ice cube while it wiggled its way into the very lowest spot of the stage area. I tried to make a machinima of the experience using the SL client feature, but I did not take time to lower my resolution from 1600×1200 for the video, and I never could find the AVI file that I expected to have made. Still, although at this point I was getting the CPUs up toward 70% at times, as soon as I cooled off and stared at the Ubuntu System Monitor, things got quiet fast, like 5% on each core.

Everything still seemed to be just ducky, until I found one more cool thing. You see, I’d been grasping about for the proper keyboard shortcuts to gain camera control on the SL Linux client. Like in Photoshop or the Windows SL client, I tend to use the keys around the space bar, Alt-, Ctl- and the arrows quite a bit. So I’ve been frustrated with the Linux client because the same Ctl-Alt combination that I want to use to spin the camera around usually does something nasty to the Gnome window when dragging the mouse. But no more. I stumbled on (what surely must be documented somewhere) the solution–the dreaded Windoze key on my HP keyboard works with the SL Linux client just the way that I expect the Ctl- key to work.

For the Linux SL client on my HP keyboard, (Alt- + Windows- = Alt- ) as the SL client works in Windows.

Once I got that grokked, I was doing some very mobile camera work for a couple of minutes, and then I tried to rez a physical sphere to see how it dropped. But it didn’t. Although my SL client was quite happy—I’d managed to hang OpenSim with this stacktrace, and now although I restart OpenSim, I can’t log in.

Native stacktrace:

../cli [0x51bb67]
../cli [0x43dacd]
/lib/libpthread.so.0 [0x7f13d3fcd7d0]
/usr/local/lib/libode.so(_Z27gim_trimesh_update_verticesP11GIM_TRIMESH+0×205) [0x7f13d06b2c75]
/usr/local/lib/libode.so(_Z18gim_trimesh_updateP11GIM_TRIMESH+0×18) [0x7f13d06b2d58]
/usr/local/lib/libode.so(_ZN9dxTriMesh11computeAABBEv+0xcc) [0x7f13d06a2a1c]
/usr/local/lib/libode.so(_ZN11dxHashSpace10cleanGeomsEv+0×34) [0x7f13d0670714]
/usr/local/lib/libode.so(_ZN11dxHashSpace10cleanGeomsEv+0×5f) [0x7f13d067073f]
/usr/local/lib/libode.so(_ZN11dxHashSpace8collide2EPvP6dxGeomPFvS0_S2_S2_E+0×39) [0x7f13d0670639]
[0x4173f5ed]

Today I would like to share the inside production notes (it’s quite low tech for the most part) on making terrain sculpties. I have included a full region’s worth of working raw terrain, and a set of four megaprim sculpties that should help to clarify some of my mutterings in earlier posts. Stuff like precisely which values go into the sculptie gradient maps (shown in a spreadsheet), what it looks like when one takes textures that are 960×960 and add a 64-pixel-extent collar around them, and how to actually configure a region to load and display the 250-meter square at Military Grid Reference System / US National Grid 10SEG_6550_9200, with all the necessary bumpmap and texture files, and instructions for both OpenSim console-side and SL client-side actions.

obdam_40h_php This is how I have created the 40 regions using MGRS / US National Grid naming convention, particularly if the terrain has been scaled to 1.024:1 so that exactly 250×250 meters of RL terrain are loaded into each OpenSim region.

obdf_2_7_f32 This is a single region’s raw float terrain file. The original input digital elevation model had been gridded to have postings every 30cm in X and Y. The nominal scale for OpenSim terrain is 1 meter in X and Y. For large grids of real-world regions, there is reason to scale things up slightly so that there are exactly 16 regions per square kilometer. When one does this, as I have here, the samples are 977 mm and the real-world scale is 1.024:1 or a couple of percent larger than life.

sculpt_gradients_132 is the magic for the sculpties, all one needs to do is take the precise spreadsheet values and create three 8-bit grayscale images from them, using a raster program of your choice, to fit 132×132 size for use as a starting point. Then in the middle 130×130 area of the Z-value image (third or blue channel), insert your 8-bit rescaled values of terrain surface. After that, stack the X, Y, and Z grayscales together as Red, Green, and Blue channels to make a single RGB that will be your UV bumpmap.

Working Example single terrain megaprim bumpmap and texture
This is a single sculptie bumpmap+texture set intended to be placed on a megaprim named ‘nw’ that is sized with ‘edit-scale nw 132 132 164′ on the OpenSim console.

Full 1.024:1-scale region with f32 terrain and four megaprim terrain sculpties This is the real deal, one of the 40 regions in the Open Berkurodam sim and I think it’s an interesting part of its steeper area. The link is to a 10MB zip file that is named for the 250-meter square MGRS/US National Grid region that it represents: 10SEG_6550_9200, the grid point at its southwesterly corner. This archive contains a single-float terrain “obdf_2_7.f32″ raw file ready for loading into an OpenSim region; the file name results from a raster dicing script and this is the second region down and seventh region over from the northwesterly corner of the 40-region sim. The archive also contains four pairs of bumpmap+texture Targa files; their file name results from the same dicing script but the indices are higher because these are quarter-region areas.

10SEG_6550_9200_xml Region configuration file for the following example (I neglected to include it above)

To try out the full region set, take an available OpenSim region, and load in the terrain from the OpenSim console with the following sequence

change-region 10SEG_6550_9200
terrain load obdf_2_7.f32
terrain bake

Next, seed the region with four prims. I tend to fly into the middle of the region or teleport and turn left 90 degrees so I am facing northerly, drop four cubes a few meters apart, then name them by their quadrant: ‘nw’, ‘ne’, ’sw’, and ’se’, ensuring that the Prim’s new names have stuck by checking at least one. Then I fly to the outer edge of the region, or just over into the next southerly one. This is not strictly necessary, but it feels like the right thing to do, sort of like walking a safe distance away after having set four large underground charges. That’s because the next step involves super-sizing. In my lab, the OpenSim server is an Ubuntu Linux box running Mono 1.2.6, but my SL client is on Windows XP, and I switch between machines on a KVM switch going from the OpenSim console to SL client, and it is so much easier to see the megaprims if you aren’t inside them after they have been inflated. On the console:

edit-scale nw 132 132 164
edit-scale ne 132 132 164
edit-scale sw 132 132 164
edit-scale se 132 132 164

The Z value is the one I use in the steepest part of the sim, and this makes some really big cubes. I tend to pull them apart far enough to tell them apart.  Be careful here–I’ve hung a sim that was running fine for a week by planting the seed prims not close to the center and then dragging the centroid of the megaprim over into the next region. Sometimes when handling these megaprims it’s handy to ensure that you have the SL client’s draw distance maxed out to 512 meters, and also to zoom the view out from default one notch with “CTL-8″ to trade of field of view with distance from the prims you are handling. So when you’ve got one of the megaprims selected for editing in the SL client, move them into position by keying locations into the Object tab while being very careful not to touch the values in the Size category (thus saving yourself a visit back on the OpenSim console to reinflate the megaprim) When using but four terrain sculptie megaprims per region, their positions in X and Y are always the same, and the Z position will depend on how you’ve rescaled your floating-point terrain to fit into the 8-bit unsigned approximation. For the example megaprims that I have posted, use these:

Prim ‘nw’ XYZ = 64, 192, 188
Prim ‘ne’ XYZ = 192, 192, 188
Prim ’sw’ XYZ = 64, 64, 189.5 (tweaked for amphitheater vs. region terrain)
Prim ’se’ XYZ = 192, 64, 188

Once I can see that the prims have snapped to fully cover the region and are all nearly the same height, I change their Building Block type to Sculpted and see four really large apples that may be somewhat subterranean. If I hadn’t already done so, I use File > Bulk Upload to get all the bumpmap and texture Targa files into inventory. When you have four megaprim sculpties, you should choose the following for Object/Sculpt Texture and Texture/Texture:

Prim ‘nw’ Sculpt = ‘ob40_03_13_z3.tga’ ; Texture = ‘ob40e_03_13.tga’
Prim ‘ne’ Sculpt = ‘ob40_03_14_z3.tga’ ; Texture = ‘ob40e_03_14.tga’
Prim ’sw’ Sculpt = ‘ob40_04_13_z3.tga’ ; Texture = ‘ob40e_04_13.tga’
Prim ’se’ Sculpt = ‘ob40_04_14_z3.tga’ ; Texture = ‘ob403_04_14.tga’

For the sort of appearance that looks best at first, I have kept the background color in the texture to all 255’s and set the Full Bright to checked. That setting does not do well when it’s night in the sim, but it overcomes some sort of fade that is visible in the texture around the edges of the sculptie when Full Bright is not set. More improvements for the future!

Deep thanks to Adam Zaius for pointing out that I hadn’t really made clear these details in the blog. Enjoy!

I’ve gotten into a groove with planting the terrain megaprims, and covered the eastern part of the UC Campus. I’ve also grabbed a video with FRAPS but it’s taking a while to upload to YouTube.

Things I learned tonight: it’s possible to crash OpenSim by dragging megaprims across region boundaries. The warning sign is that the prim appears to lose its name, then all prims in the region lose their names, then a check of the console will show no more OpenSim running!

After a couple of technical issues, I am pleased to offer some machinima views

This is a shot starting at the Greek Theater on the UC Berkeley campus (20080430)
http://www.youtube.com/watch?v=86IVMafq3ik

This is simply how the Open Berkurodam sim looks in its overview map with 40 Regions.
I haven’t refreshed the appearence of the map since loading in the real-world terrain (20080430)
http://www.youtube.com/watch?v=hvGLmtTY0uI

This is a flight eastward over some bare ground, but real-life terrain regions. Flight is in the vicinity of BANCROFT AVE between SHATTUCK AVE and TELEGRAPH AVE (20080430)
http://www.youtube.com/watch?v=56PfQp9viqE

This is a flight into the land of Terrain Megaprim Sculpties.  Of the three scales, this shows the medium and large steepness areas in easterly campus.  At the time this was shot, there were fifteen regions with 60 megaprim sculpties in a contiguous area (20080430)
http://www.youtube.com/watch?v=Q9cElvejrxo

This is a flight from the high point of the sim starting at Lawrence Berkeley National Laboratory, over the Greek Theater, and ending near Wurster Hall at UC Berkeley (20080501)
http://www.youtube.com/watch?v=uBlbB72cpUQ

This is a flight starting near the old Pacific Film Archive building, through an excavation at Underhill Field that was open on 1 July 2006, then up PIEDMONT AVE to GAYLEY AVE past California Memorial Stadium and up to the far NEly corner of the sim in LBNL (20080501)
http://www.youtube.com/watch?v=cealA1QL59s

Enough Videos already!  While you’re at YouTube, check out “OpenSim” as a search term, if you haven’t already!

There has been a bit of head scratching as other distractions apparently clouded an obvious scale issue. The first terrain megaprim sculptie project done last month, had available imagery at 30cm.  For that, it only made sense to oversample to 25cm to make 512×512 textures.  That decision led to my adding a collar around the original 512’s until they clicked into the proper size without rescaling on a quarter-region megaprim. With Berkeley, the source imagery is almost 10cm (103mm pixels) and the challenge has been to size the resample so as to make best use of the 1024×1024 texture size limit per prim.

Where I took a wrong turn was trying to proportion the collar that was added to the 512’s, rather than going back to basic principles with sculpties. Bottom line: my efforts of the past week went astray as I allowed confusion to set in, casting about for the proper maximum texture dimensions working down from 1024. (and I’ve got the awkward attempts at 1008, 994, and 978 pixels to prove it).

In fact, the answer is very simple in reference to basic sculptie principles, as the maximum dimensions of the sculptie bumpmap are 32×32, and due to the need to wrap it around to an apex underneath, this can only represent a 30×30 terrain patch. Thus, the maximum imageable area is simply (30/32)*1024, or 960 pixels square, collared out to 1024 square to make each orthophoto tile. This means that an OpenSim 1.024:1 model can accomodate 130mm orthophoto imagery, and I now have 160 tiles ready to go with the bumpmaps.

So far I’ve configured twelve regions with their megaprims, and only one seems to have issues with the height of the sculptie to stay 30cm afloat the terrain surface. Nine of these reigons use the flattest setting, one uses the intermediate, and two use the steepest. Here’s some shots for update’s sake. The full set of orthophoto textures have been uploaded (450 MB of Targa files) and seem to show up reasonably well in inventory. I am using a local MySQL instance on the OpenSim machine for prim storage.

After spending plenty of time getting all the terrain megaprims stamped out, and starting some refinements of how to squeeze the imageable part of the ortho into a portion of the 1024 square texture, I found myself rather unhappy with how lumpy the megaprims were in the flat part of the model. Berkeley has this sort of dual terrain personality (no comment on the residents) that has certain types of details in the distal fan and floodplain parts of town to the westerly, and very different types of details in the hilly and steep areas.

When one loads the natural terrain into OpenSim, the values are 64K of single-precision floating points per region. When loading terrain into a megaprim, there are a mere 900 usable values that must be mashed into an 8-bit integer of Z values. So when the whole sim ranges from 45–267 meters (and it could go up to 581 meters if a sim ran all the way up to Vollmer Peak) , one gets dynamic range issues if all the terrain megaprims are scaled to fit over the entire sim. So to mitigate this, I divided the sim into distal (the “flats”), proximal (the “foots”) , and hills proper (easterly of the Hayward Fault).

The upside of this extra work is better fidelity in the different parts of the model when the floating point values are approximated by 8-bit integers. When I used the entire elevation range for the whole UC Berkeley sim, each integer Z value was 87 cm, or close to three feet. With the sim broken into three regions of megaprim Z-scaling, I have each integer worth 11 cm in the distal, 31 cm in the proximal, and 63 cm in the hills, so everything is a little better everywhere. I’ll fess up to not having the prim placement fully automated, otherwise it would be practical, and perhaps desirable, to use the full dynamic range over just those elevation values in the region (or even in the quadrant of the region that the terrain megaprim covers). But by that point, I’d consider even denser grids of terrain megaprims, and it would then be a different process for representing the terrain.

After all, the whole point of this exercise is to devise a work-around for not being able to load the ortho imagery directly into the region as a draped terrain texture!

Enough blabbing - please enjoy the graphics.

Here is how the terrain maps out versus the buildings

Not intended as digital Cubism, this odd-looking approach makes better terrain megaprims. Really, it does!

In case one knows particular buildings on the UC Berkeley campus or environs, this is how the zoning worked out. There is a certain logic to it, geomorphically.