Convoys and Formation Command

[IckyATLAS]

I have been experimenting lately with ship and train convoys and try to understand some of their weird behavior. This finally has allowed me to understand some underlying patterns.

 

Let's first see what we have in the ME. In the editor it seems that only Vehicles,  and Planes have been considered. In these two cases you can have a leader (or flight leader) and all the members of the convoy are Target linked to the Leader. If we look to The MCU Formation command we see that only Planes and Vehicles are mentioned, and they work pretty well. For Vehicles you have the OnRoad, OffRroad, user formation etc. and it does give us basically all we need. For planes I would have preferred more options mainly for large bomber formations but who knows maybe in a few years ? 

 

What about trains and ships ?

For those who do not want to read further a simple fact: the only way to have a perfect convoy of ships or trains (multiple separate trains moving in concert) behave as they should, is to have for each ship or train their own set of waypoints. You have complete control on the convoy behavior. By having waypoints of one element of the convoy  acting on the behavior  of the other elements of the convoy you can do very complex stuff.

 

What is the big difference with trains and ships. The Trains are constrained by the railtrack and cannot step sideways. So the fact of target linking trains does work, but as I said in a different post you have to take into account the weight of the trains as this will impact acceleration and speed. This makes it nearly impossible to have trains following each other at short distance except if they are identical but still you need enough separation to avoid a collision against the leader when it stops. And when the leader train stops all other stop wherever they are.  Not perfect but works.

 

The Ships on the other side are free to move in every direction and they do so like the vehicles do when they try to avoid one another. The problem lies here in the way the passing of a waypoint is made. As long as the ship waypoints are  perfectly aligned with the same speed target, and all ships can go at that same speed the convoy will move on keeping formation I mean distances between ships without much change. They will stay one behind the other with minimal disturbance.

 

The disturbance lies in the way the point is passed. The way it is done seems very crude and we do not have nice interpolated curves between straight segments. As a result when there is a turn the leading ship on the waypoint slows down (yes his sped in the same direction goes down as he changes direction) as he is turning. The following ships trying to keep the straight line distance separation turn immediately with a lateral avoidance move. This avoidance move is made even if they have a huge distance between them without any risk of collision. When the leader is stabilized on a new direction they turn again and slowly come back in line with the leader. But if the leader has multiple turning points in shorter intervals (I mean so that the ships behind have no time to come back inline) then the ships behind enter in fully chaotic turns and move completely erratically. This is really an example of very poor programming here. B-Splines would be ideal to generate the proper constant speed nice curved turn trajectories.

 

What about using the Command Formation with the following mode Vehicle: Off Road Column. This is the right mode to use here. We will put the distance to Loose so as to have maximum separation. This Command is made for vehicles. They are much smaller in size and so distances between vehicles defined by Dense, Safe, Loose are not the right values when working with large ships, but it works up to a point.  So what happens?

 

Ships stay in column and turn in column only when they reach the waypoint and follow gently the leader. Excellent you may say. The problem is that the formation command will manage distances between ships as with the vehicles. So if your ships are say a mile apart, the ones behind the leader will speed up at unrealistic speeds (speeds they cannot do) just to close the gap and be at the Loose distance for vehicles. You can imagine with tankers this means they are maybe 50 meters max between the bow and the stern at best, and if there are speed differences between waypoints they will collide. If there are ships of different sizes that means they accelerate or decelerate differently then it is even worse. They slower they go the better it is. If you have say three destroyers at 30 knots and they are far apart, the ones behind the leader will accelerate at 60 knots maybe and close the gap but then will take time to decelerate and so will bang in each other.

 

But if you make  a convoy of torpedo boats that are much smaller then all is fine. Separation between the torpedo boats becomes acceptable and you can have a very nice convoy following properly the leader. But again when the leader stops all the ship stop where they are.

 

I hope one day in the future they make for us at least two Formation commands for ships:  Ship: Column, Ship: User formation, and with proper Dense, Safe and Loose distances. 

 

 

[jollyjack]

Been experimenting with 5 riverships in convoy ... only the leader in formation stays afloat, the rest beaches a on the banks. I'll try separate waypoints ...