reported How to make a naval version of any SAM system (using a bug)

meltingSnowdrift · November 10, 2022

Procedure to reproduce

Run the attached mission files. They contain only AI units.

The mission file "demonstrator 1" is a simple demonstration of the basic bug. I think it is close to the minimal mission contents needed for this bug to work.

The mission file "demonstrator 2" is a more elaborate demonstration showing a full SA-5 missile system engaging in combat while mounted on a group of moving boats.

Suspected principles

Static land units and non-amphibious vehicles (hereafter "pure land units") must be placed on land.

Earlier testing showed that, if an amphibious vehicle is placed on a ship, that vehicle travels with the ship. Placing something on a ship, for our purposes, means that the reference position of a land unit (the centre; the point within the model of the land unit corresponding to the centre of its icon in the mission editor) overlaps with the ship's model.

This result led me to suspect that, if a way could be found to place a pure land unit on a ship, that pure land unit would travel with the ship as well. This suspicion was confirmed.

In the mission editor, ships and boats can only be placed on the sea. They are only capable of motion if they are not aground. Vessels with shallow draft, such as the speedboat, are capable of motion even when placed extremely close to shore because they need little depth to float and move.

In certain locations in the ports depicted in the Caucasus map, the boundary between land and navigable sea is extremely sharp and steep. This causes there to exist a narrow region at that boundary where pure land units can be placed but which can also be occupied by a small part of the model of a speedboat without immobilizing that speedboat.

It is thus possible to fulfil the condition for making a land unit travel with the speedboat even when that land unit is not amphibious.

Expected behaviour

The series of tests leading to the discovery of this bug was conducted with the purpose of finding exactly such a bug. Unusually for my bug reports, there is therefore no expected behaviour differing from the actual behaviour. See the "Opinions" section for further context.

Actual behaviour

The image below is a representative example of the results of successful use of this bug.

When this bug is applied to static land units, they become rigidly attached to the boat in all dimensions. Static land units in this condition are upright relative to the boat.

When it is applied to land vehicles, the results can be highly unpredictable. Sometimes, possibly when the land vehicle does not try to move, the result resembles that for static land units except that the land vehicle is highly tilted. Other times, possibly when the land vehicle does try to move, it appears to try to move on an invisible tilted plane rigidly attached to the boat. Under unclear conditions, land vehicles in this condition can also teleport short distances (within visual range), after which they continue to move on a plane rigidly attached to the boat.

Sometimes, as shown in the image above, land vehicles become raised into the air while remaining rigidly attached to the boat. This may be possible (as I suspect it was in this case) even if the vehicle does not try to move.

Opinions

(Unlike the rest of this post, this section expressed my views rather than factual claims. I separate these views into this section to preserve the clarity and professionalism of the bug report.)

Though I acknowledge that the behaviour I report is unambiguously a bug, I feel that it may be better to think about it as something more than a problem with the game. It reveals potential in the game that is presently underused and which I suspect would not be hard to fulfil.

The direct mounting of originally land-based military equipment, including SAM systems, is a practice with recent precedent[1] in real life. Inspired by this and by experimenting with existing functionality for placing static objects on ships, I began to wonder whether functioning land units could be placed on ships as well. Though it was almost immediately apparent that this could not be accomplished using the current intended behaviour of the game or the mission editor, the possibility captured my imagination. The resulting hours of experimentation produced the results presented here.

Treating this behaviour as a pure bug, I expect that it would not be hard to fix: one would merely need to make it impossible for any land unit to rest on a ship. I propose, however, that no more than a little more effort would produce a result much more friendly to the creativity of a mission designer.

I specifically propose to allow the placement of pure land units on the decks of at least some ships but to make land units in such a state immobile relative to the ship. By rigidly attaching these land units to their ships, most of the potential for serious misbehaviour described in this report (teleportation, motion along invisible planes) is removed. As demonstrated by the bug and by the ability to place static objects on ships, the fundamental features required for this functionality are already present. It should therefore require little implementation effort, especially compared to the tactical and storytelling possibilities it opens.

[1] https://www.thedrive.com/the-war-zone/russian-black-sea-warship-now-equipped-with-ground-based-sam-system

demonstrator 2.miz demonstrator 1.miz