Blake Sea and Le Tigre
You probably remember the region crossing problems sailors and pilots had with the previous Havok Physics Engine update. Putting different versions of Havok on adjacent regions creates problems. Havok was never designed for use across multiple versions of Havok. It’s use by Linden Lab™ is the only known use that encounters that problem. So, we will likely have crossing problems with each update of Havok.
With the addition of Pathfinding and possible other gaming features to Second Life™ we are likely going to see more updates of Havok, but fortunately, less crossing problems. ‘More’ is like a couple a year.
Some weeks ago the Lab tried placing adjacent regions in the same or adjacent servers, physically adjacent servers. This made what Oskar Linden described as a ‘MASSIVE improvement’ in performance. Now it is standard operating procedure to keep the regions and servers organized.
The consolidation of 3 data centers into two has caused some disorganization. So, another pass of reorganizing is in progress. We can see that effort as additional region restarts. It takes 2 restarts to move a region. I don’t quite understand why, but a limited number of spare servers contribute to that necessity.
Oskar says they shut down and brought up in groups. I suppose the group count and number of spare servers are where they run into some limits. If I understand correctly, the solution has been to move the group into spare servers. Then the target servers, which are often already full of regions, are emptied as those regions are moved out. Then the group can be moved into the just emptied target servers.
Manual restarting of regions should not break the organization of regions, so says Oskar. I am supposing that as things are organized subsequent version updates return regions to their proper place.
The first reorganizing took six weeks. Maestro Linden says this one is expected to take less time as the process is starting from a ‘less scrambled’ state.
Part of the reorganizing in this pass includes getting some adjacent regions into the same server version channels.
There are 4 or 5 channels to which regions are assigned. The main channel runs the main production code and makes up about 80% of the SL grid. There are 3 Release Candidate channels; Blue Steel, Le Tigre, and Magnum. The RC channels get the test code that is in final Beta testing. There are also some special channels that come and go which are used for special test projects.
Channels are a list of servers that the updating software uses to determine which server gets which version of the simulator software. Part of this server reorganization has included reworking the channel lists so adjacent regions with high vehicle traffic are moved into channels with the same Havok version.
That doesn’t mean all vehicle traffic regions go into the same channel. It does mean the Lindens are trying to get regions like the Blake Sea and Dune Buggy regions into matching Havok versions. While sailing in the Blake Sea one should only encounter a single version of Havok. The Dune Buggy regions should only have a single version of Havok, but not necessarily the same version as the Blake Sea regions.
On Thursday I got the impression from Oskar Linden that Blake Sea regions were being moved into Le Tigre. It apparently didn’t quite work out that way. On Friday Andrew Linden was looking to see how the reorganizing has worked out. It seems the Blake Sea area was moved into the Main and Magnum channels. Previously a number of those regions had been in Le Tigre.
I think it was Simon Linden that commented looked like trying to move all of Blake Sea regions into Le Tigre would have been a problem. So, it seems operations took the easier path. Whatever the case, the heavy vehicle traffic areas should have more consistent Havok versions and fewer region crossing problems.
The Havok Difference
This version has enabled Havok’s “Collision Geometry Optimizer” for the terrain. There is a terrain mesh that we see in the viewer. Havok takes that mesh and simplifies it. The simplified mesh something we don’t see. Our avatars and vehicles walk/drive on the simplified mesh because that is what Havok uses to calculate collisions.
The Optimizer further simplifies the terrain model. We should see smoother terrain… less bumps as the Havok engine has fewer triangles to deal with. \
In general we still can’t see the physics terrain model. If we open the Pathfinding Navmesh viewer, we see an even further simplified terrain model. Maestro says if we look at ‘walkables’ we might be able to notice some additional simplification. But, I suspect unless you are looking for the difference you are not going to notice the appearance change.
We should get better performance from the update. Whether it will be at a perceptual level or just something to measure with a stop watch… I’m not sure.
Earlier I had information on the new OBJECT_PATHFINDING_TYPE’s. They goofed and misspelled a type name in the announcement: OPT_UNKOWN, which they intend to correct to: OPT_UNKNOWN or possibly: OPT_OTHER.
There is a crash problem in Le Tigre. That update will not roll forward to the main channel in week 43. So, the Havok and potential region crossing problem will continue for at least another week.