#1: Elements and protection values Author: ScnelleMeyer, Posted: Thu Oct 20, 2016 1:02 am — I asked about how Cover and protection values from Elements.txt are implemented by the game engine at Matrix forums.
Steve McClaire gave a very solid answer that I am reposting here for modding reference.
"Cover is checked against the accuracy of the shot to determine if the shot hits the terrain or not. The higher the cover value the more likely the terrain is to protect the soldier. There are a number of modifiers to this, most importantly the 'in elem protection flag,' but things close range, weapon type, movement, etc. are a factor as well. The best possible cover would be to set 'cover' to 512 in all planes and set 'in elem prot' to 1 (full cover, all directions.)
Note that 'Good' and 'Critical' accuracy shots bypass terrain protection completely. The chance of getting one of these types of hits is reduced by the cover value, but they can still happen even if you put cover to max. So soldiers may still take a lucky hit that bypasses terrain protection.
The 'planes' are how high something is for LOS interaction purposes. This is used to determine if the LOS line intersects with the terrain feature using a very simple model of 3D space and heights.
prone <= 0.5m
low <= 1m
Med <2m> 2m
The exact 'plane' which is used to see if terrain is in the way depends on both the relative elevations and stances of the firer and the target (prone, crouch, stand, vehicle.) Imagine a 3D line from the plane of the firer to the plane of the target, and the height of that line is checked in a very simple manner (via which 'plane' it is currently in) to see if it intersects any cover in between them.
Example: Two soldiers are lying prone and both are at the same elevation. The 'prone' plane values would apply when checking LOS or determining cover. Now say the firer is in a two story building and the target is prone at a relatively short range (close enough that the LOS calculation comes down at a relatively high angle instead of flat across the map) -- in this case a higher plane would be used, depending on how 'high' the LOS line is when it crosses any obstacle between the firer and target.
Keep in mind that CC's notion of 3D space is very simple and not very granular. Also the way the 'fire' order line is determined and displayed is not as detailed as the method for checking cover when one soldier fires at another, so you can see discrepancies.
