SLRR and VRC script changes needed for rail lines in Bellisseria

[arabellajones]

I have made several test runs with a locomotive of mine on the SLRR-compatible rail lines of the Bellisseria continent. Much is still unfinished, but usable. The main problems are the limited number of rez-zones and a few unreliable region crossings. There's also a difference in the Land Permissions which means multi-unit trains need to be built as a single vehicle. The follower-vehicle method used by many scripts fails. Anyone building a tender locomotive needs scripts which fix this

The main section is a loop running through Pugwash in the west, with a very long spur to Bridle Path in the north-east. There are two branches running to the south coast, both with nearby docks, and a junction at Gully Wash for a line to the north coast which is clearly expected to be extended, the same sort of sharp cut-off of scenery you get if the adjacent region is down.

There is also a Chalet sub-continent line, mostly following the Big River, from Hydrant to Lavon, again with likely extensions at each end.

I have found that Land Impact can be critical in getting reliable operation. Many of the older VRC and Hobo freebies are very old, prim-heavy tech. I have managed to get a mesh version of a prim-based model from LI=27 to LI=8, and it has improved running.

Some places have rather suspect track design, features such as sharp curves at region crossings (there's a bad one just south of Gully Wast). I have a suspicion that it needs a change to the locomotive script to fix. I am going to increase the SENSOR_SEEK_ARC_DEFAULT but the paucity of rez zones is going to make testing tedious. Since there are similar failures on dead-straight sections of track, in mid-region I shall also try increasing SENSOR_SEEK_RANGE_DEFAULT

I am working, fitfully, on a model of this, to allow high-speed passenger services on the Bellisseria lines.

I will note that many of these Bellisseria lines run through regions with an SSPE label, which Linden Lab regard as officially unfinished. But the Chalet section has blatantly unfinished track (look at Lavon with visible guide prims) in named regions.

[arabellajones]

I have now being able to check the increased SENSOR_SEEK_ARC_DEFAULT at the boundary between SSPE1124 and SSPE1125 which has been one of the black spots for me. The northbound crossing actually worked for me with a value of 30.00 and I have not yet seen other problems. But I am not sure because I have seen that Squeaky Mole has added two extra guide prims, the long ones you see in the picture. It looks as if they would reduce any sensor angle problem. 

The rate of change for the short prims is, as near as I can tell, marginal for a 25-degree sensor arc. The SLRR specification for curves is not all that clear, but I read it as saying more than 15 degrees in 10m needs caution. Trouble is that the region crossing process adds delays to scripts so the critical sensor ping could completely miss.

[Qie Niangao]

4 hours ago, arabellajones said:

There's also a difference in the Land Permissions which means multi-unit trains need to be built as a single vehicle. The follower-vehicle method used by many scripts fails. Anyone building a tender locomotive needs scripts which fix this

Yeah, this land setting (disallowing Object Entry) means that only sat-upon objects can traverse the path, which for my interests renders railway throughout Bellisseria ornamental at best. Among the problems are multi-unit trains, as you mention, which can't really be "fixed" in any practical way, inasmuch as all the units would need to be linked in a single assembly, requiring a whole lot of geometry calculations, especially complicated for curves at or near region borders. That's assuming that such a complex assembly of links can make it across the border at all.

Anyone who's looked at the VRC train scripts knows they could be much simplified, in part because they antedate many "efficient script" functions for manipulating link properties. I've sometimes been tempted to tidy-up, but I always worry they may unwittingly depend on accidents of timing.

[arabellajones]

4 hours ago, Qie Niangao said:

Yeah, this land setting (disallowing Object Entry) means that only sat-upon objects can traverse the path, which for my interests renders railway throughout Bellisseria ornamental at best. Among the problems are multi-unit trains, as you mention, which can't really be "fixed" in any practical way, inasmuch as all the units would need to be linked in a single assembly, requiring a whole lot of geometry calculations, especially complicated for curves at or near region borders. That's assuming that such a complex assembly of links can make it across the border at all.

Anyone who's looked at the VRC train scripts knows they could be much simplified, in part because they antedate many "efficient script" functions for manipulating link properties. I've sometimes been tempted to tidy-up, but I always worry they may unwittingly depend on accidents of timing.

That complexity is why I suggested a tender locomotive. A GWR Autocoach could soon get too complicated.

[arabellajones]

I know some of the people reading this are rail geeks, but some aren't. So a few pictures of things that could be handled as articulated vehicles

This is on the Heterocera line, a Y6 Tram Engine with a passenger coach. The history is a bit complicated. but the tram engine is simpler to make a model, because all the moving parts are hidden so as not to scare the horses. The locomotive and coach are similar enough size that the basic SLRR/VRC method of putting the vehicle centre on the Guide prim works.

This is a tender locomotive, and while the proportions are a little different, the tender is not so different from the coach of the first picture. The wheels and coupling rods need animating, but this isn't so complicated because of the inside cylinders. This general type of locomotive was very common across Britain, though this is a WW2 design made to use the minimum of materials. While many earlier designs had more open cabs, the old two-vehicle approach might not work well.

This is an Autocoach train, and this would be where things get tricky. It's running right-to-left, not the usual flip we get from the VRC script, and the driver is operation the train from the far end of the coach to the locomotive.  But it's the length of the coach which is awkward. It's a 70ft long bogie coach, and that is so much bigger than the tank locomotive. I am not sure it would be practical.

This would be a better answer for passenger trains on Bellisseria, the basic idea was being tried in several countries before WW2. This is a diesel streamlined railcar of the GWR, and while the guide-prim details for such a long vehicle could be awkward, it's still a single vehicle. At least initially, the bogies were shrouded. These were fast, rather opulent, trains. Some of the early ones had a buffet/bar. Unlike the autocoach solution it wouldn't much matter if you used the old-style Flip to reverse travel.

 

Anyway, some pretty pictures to inspire you, and some idea of the options. To get the right proportions on standard SLRR, with the broad gauge, these coaches would be around a nominal 30m long. That suggests as much as 45-degree change in direction in the overall length. I don't think a simple guide sensor at the vehicle sensor would work. Some sort of sensor at each bogie position, and applying the mean of the two positions and directions might work.

 

[Candide LeMay]

On 8/22/2021 at 5:26 PM, Qie Niangao said:

Yeah, this land setting (disallowing Object Entry) means that only sat-upon objects can traverse the path, which for my interests renders railway throughout Bellisseria ornamental at best.

Are these land settings like that on purpose or is object entry something that could be lobbied for with LL?

[Qie Niangao]

1 minute ago, Candide LeMay said:

Are these land settings like that on purpose or is object entry something that could be lobbied for with LL?

Someone could ask @Patch Linden if there's any prospect of changing it. A couple of reasons they may choose to keep Object Entry disabled:

1. Reduces certain kinds of object griefing, and hence the overhead of Governance sometimes needing to get involved.
2. Some folks really hate autonomous vehicles in SL, and historically there were some that had problematic behavior and resource use.

I was once told that when Zindra was new and most of its road network and waterways were similarly nerfed, it was to prevent one specific creator from running her (especially troublesome) autonomous vehicles on the then-new continent, so similar thinking may apply to Bellisseria. 

Another adult content enthusiast and I had a notion of introducing a Zindra-integrating ferry service to navigate through the waterways and shorelines, but no-object-entry thwarted that idea. So much of Zindra's promise was lost, however, for so many reasons that it's hard to claim enabling Object Entry would have made any difference.

[arabellajones]

32 minutes ago, arabellajones said:

Anyway, some pretty pictures to inspire you, and some idea of the options. To get the right proportions on standard SLRR, with the broad gauge, these coaches would be around a nominal 30m long. That suggests as much as 45-degree change in direction in the overall length. I don't think a simple guide sensor at the vehicle sensor would work. Some sort of sensor at each bogie position, and applying the mean of the two positions and directions might work.

I goofed here. Many of the passing loops  have an S-curve at the switch, so the guide prims at the bogie positions could be parallel. The mean of the positions would work for the position of the centre of the vehicle, but you would need to calculate the vector to get a good direction. The angles might not not be small enough to use the small-angle approximation, but the error may only show briefly. The SLRR gives 8m distance between parallel tracks so I think the approximation should work.

I think I am going to go and have a quiet headache, "llSensor does not detect objects or agents across region boundaries"

[Quistess Alpha]

6 hours ago, arabellajones said:

"llSensor does not detect objects or agents across region boundaries"

my immediate reaction to that is to set-up a communication protocol rather than using llSensor() on the train itself.

ex: train shouts: "get guideprims" and a relay in the next region shouts back the needed information from all the guide prims. (or, if you want to be more conservative, get rid of the guide-prims all-together, and only use them as a part of the setup process)

[Abnor Mole]

6 hours ago, Candide LeMay said:

Are these land settings like that on purpose or is object entry something that could be lobbied for with LL?

It has to do with the house rezzing system set up in Bellisseria for Linden Homes. Linden Homes are touted as "the house doesn't count against your parcel LI" which they don't. That doesn't mean the houses are 0 LI. They are actually as much as 250LI. They just have their root on the main parcel along with all the other deco content and are technically "owned" by us, not the resident. To facilitate this we have to keep a buffer of LI in reserve on the main parcel for the rezzing of houses. If the main parcel becomes too full we could have situations where a resident switching homes would not be able to rez one because the LI of the main parcel could not support it. If there was (for example) a 500LI train using llMoveToTarget to pull carriages along behind it cruising through the region and someone attempted to rez a house... no house would appear. To keep this from happening (and to help prevent mischievous residents from trying to force it to happen) the main parcel has a short 1 minute autoreturn and does not allow rezzing outside of a rezzing zones or allow objects to be moved into it from other parcels like rez zones, resident parcels or neighboring regions.