One racetrack, a little over 4 square kilometers of space (or 4,194,304sqm). This is my first attempt to build something with a bit of scale to it, now that we’ve got mega-regions working in OpenSim. (and vehicles.)

To start with, I need a terrain large enough to encompass the entire area (there’s no way in hell I’m manually terraforming this one) – courtesy of DeepThink, I have a license to World Machine Professional, a commercial terrain editing package that absolutely kicks ass. World Machine builds terrains in a semi-layered manner, then allows you to combine those through a railroad-style filter scheme.

Grabbing one of the World Machine samples as a base (since it had road layers already setup), I modified them and redrew the paths to build a 16×4 sim (4096×1024) terrain and rendered it. You can see the output in World Machine below, of course from this scale it doesn’t really do it justice.

Travelling at 55.5m/sec (200kph, 124mph) – you will cross into another region-sized space every 5 seconds; but the total racetrack length means that even at this speed it will take over a minute to complete, encompassing a minimum of 16 region-sized areas, which in turn is only a small subset of the entire space availible. Taking a picture of the terrain loaded into the mega region, you can see just how insignificant an avatar is at this scale.

This is compounded by the fact that the viewer refuses to put it’s “farclip” beyond about 4 sims distance, so at best you can see 1/4 of the track at once. The ringworld walls are each about 150m tall at this scale; and geographical features are quite recognisable as geographical features.

Of course, we can’t just leave it at that – to quote Mythbusters, “if it is worth doing, it is worth overdoing”, so I pulled up the terrain in world machine again, and decided to go a little bigger. I originally made it at 48×4 sims, however had to crop back to 32×4 due to my machine needing more memory to do the resulting 12,288 x 1024 terrain without swapping on disk constantly (resulting in a multi-hour render). For scale reference, the smaller of the two circles is about the dimensions of a single normal region.

Part 2 will cover texturing and detailing this race track, followed by some first impressions of how it behaves with Kitto’s new vehicle patches. Once I’m done with it, it will go up live on the Hypergrid (and probably OSgrid) for public perusal.

Kitto Flora deserves some major kudos for recent developments with OpenSim vehicles. Not only do they work, but the revised car script I toyed with earlier today – was actually quite usable; and dare I say it? good. All of this is thanks to Kitto’s work refining and improving the vehicle functions and how they interrelate with the internal ODE physics engine.

I could speculate here, and say if you were a decent vehicle coder – you could probably do some amazing things with OpenSim these days. So what happens if you combine these new vehicles, with Teravus’s recent mega regions code, and my sculpty terrain code (with mods from nebadon)? This. (Recommend jumping to about 4:40)

(Edit: Added a new link to the video – 22/09/09)

I probably do not need to go into too much detail here – the above is a 3_x3 megaregion, using 576 physical sculpts, Kitto’s latest ODE mods & vehicle script – running on a home users cable connection; with several people driving around at once. Not only does it work – it suprisingly works well. I expect a more skilled texture artist could pull some amazing things off with the sculpty terrain code – the terrain is just a quick output from L3DT done by Nebadon.

The vehicle code isnt in trunk quite yet – but if you ask around in #osgrid, I’m sure someone can point you to the github account where you can get the ODE patches. I’m sure much like mega-regions, it will be in trunk soon enough.

Credits: Kitto Flora (vehicles), Teravus (megaregions), Nebadon (video, hosting, testing, sculpty terrain), Bri Hasp & Hiro Protagonist (hosting & testing), Myself (sculpty terrain generator).

So that post on Megaregions ended up being a bit more popular than I imagined – resulting in a veritable torrent of ‘How do I enable megaregions?‘ requests both to my personal inbox, the #opensim-dev chatroom and the opensim-dev mailing lists. You can stop now. Here’s instructions.

It’s actually really simple if you are running the latest experimental code, however I need to prefix these instructions with a dire warning: this is very new code. The first prototype was done on August 28th.  It’s been a week and a half since then. Yes MegaRegions are an exciting bit of technology, but no – they are not that well tested, and yes there are bugs. More than usual. It was added to OpenSim as a undocumented feature because Teravus (in his right mind) didnt want to inflict it on the masses until it had at least a modicum of testing among more experienced users.

There are known issues at this stage – do not attempt to convert an existing array of regions into a single Megaregion without taking a full backup first (apparently there are issues there too) – if you still want to go ahead and check this out; you need to be running a relatively recent Git release of OpenSim (warning: there be dragons here already), into your OpenSim.ini add the line “CombineContiguousRegions=true” under the [Startup] section, eg:

[Startup]
CombineContiguousRegions=true
...

The regions need to be contiguous (that is already bordering), and you need to order the regions in your Regions.ini in a Left-to-Right, Top-to-Bottom (Correction: South-to-North, West-to-East) order. Failing to order the regions will cause the combiner to fail (new code. known issues.); it is recommended to make new regions for the purpose of this exercise. Otherwise, this is a fairly simple process to those already aquainted with setting up OpenSim regions. Credit goes to Teravus for the original implementation.

Grid etiquette right now suggests it is best to not connect megaregions neighbouring to non-megaregions for the moment, as they may introduce instabilities into your neighbours. (eg, pick random numbers for your starting coordinates). While you can connect megaregions to grids such as OSgrid, please do so away from the main continents. For loading a terrain across all the regions, I recommend investigating the “terrain load-tile” command, which allows you to import multiple regions worth of terrain from a single image. The above terrain was generated off a 2048×2048 F32 RAW produced by World Machine.

One of the single most common requests for OpenSim has been “I want bigger regions” – coming originally from an ActiveWorlds background, I wholeheartedly agree.

Space is still a major constraint – and while OpenSim allows you to run multiple regions within a single simulator – it’s a poor comparison because crossing region borders, even within the same machine are a complicated and error-prone process; requiring the client to disconnect and reconnect at least once. This preventing any kind of “instant” handoff on a technical level. Megaregions are a new bit of code that solves this problem by side-stepping it (a.k.a cheating).

Regions within the same simulator process can be ‘combined’ via the new RegionCombinerModule; to the client all the regions that existed in the server previously become ‘neighbours’ rather than full regions in their own right; while the original region takes authority over the combined original space. Objects get coordinates that no longer resemble 0,0-255,255, they now can reach values such as “1077,2099″, and likewise your avatar and any positional coordinates you see reflect this new larger domain.

The result is you can use these combined regions to make ‘megaregions’ that exceed the original 256×256 bounds. I personally have tested both 512×512 and 2048×2048 regions (comprised of 4 and 64 original regions respectively) and it is awesome. For vehicles I can see this being a very impressive and useful new feature – eliminating border crossings makes for bigger racetracks and faster speeds. Sailors can build oceans that aren’t equivilent to a lake-in-the-backyard, and if my estimate of 5MB per empty region holds true at scales larger than 64 regions in size; then it’d be possible to build a 4km x 4km ocean on a server with less than 2GB of RAM (equivilent to about 256 sims normally).

Pictures are of course essential for this post – the first picture below has me selecting a 65,536sqm parcel for comparison — everything you can see in the picture is but a small fraction of a single region. (11 cells are visible, of a total of 64)

…and a slightly larger picture of the same sim showing a few more cells at once.

Finally, I recorded some video of vehicles playing around on one of these megaregions (from a slightly earlier version when the largest regions were a bit smaller). This is in OpenSim trunk now; however it does have some known issues – so I wouldnt do anything resembling production work on this code for a long while until it has been more properly tested. I’d like to do some more testing with this and vehicles at a later date however, as OpenSim/ODE’s support for vehicles has improved dramatically in the last few months.