[http://sourceforge.net/p/ufoai/feature-requests/345 Item 345] imported from sourceforge.net tracker on 2013-01-28 20:18:20

There is a related thread on the forums here:
http://ufoai.ninex.info/forum/index.php?topic=2789.0

The underlying system is simple conceptually. Each wall/obstacle would have a certain 'absorption' value. This represents how much damage an obstacle can absorb from a projectile capable of penetration. If the absorption value for a given obstacle is exceeded by a penetration capable projectile, that projectile will travel through the obstacle, and its damage will be diminished by an amount equal to the exceeded absorption value.

Note that not all projectiles are capable of penetration (most plasma and contact detonation ones for example), and those that are not will not travel through an obstacle regardless of how much that barrier's absorption value is exceeded.

Furthermore, attempting to fire at a target through an obstacle with a soldier that does not have a line of sight to the target will result in signifigant accuracy penalties for obvious reasons. The spread of shots made against targets by a soldier who does not have LoS to them will be increased dramatically (2-4x).

Other elements of the system include additional spread multipliers derived from the distance of a soldier from a penetrated obstacle between him and his target:

The mathematical basis for accuracy loss/spread multiplication as defined by distance from a penetrated obstacle might be (250 - Distance) / 125 = Spread Multiplier. I selected 250 as this is the maximum range found on any weapon, and 125 as the divisor to limit the max/min range to 2-0. This spread multiplier would 'stack' with the base penalty for attempting to shoot at a target you do not have LoS to through an obstacle. For example:

Base spread with an aimed assault rifle shot is 1/1. Trying to shoot an alien through a wall would increase the spread by a factor of 2 (let's say), to 2/2. Then, because the distance between you and that wall is 4, the spread would be multiplied again by 1.968 ((250 - 4) / 125) to 3.936/3.936.

Finally certain types of ammunition are better able to penetrate obstacles than others. A set of coefficients could be used to determine and model the specifics of a munition's penetrative qualities. For example, a 'power' coefficient of 2 for a round/ammo type would mean that round has twice its regular power for the purposes of penetration, while an 'efficiency' coefficient of 0.75 for a round would mean that only 75% of an obstacle's absorption value applies for the purposes of reducing that round's damage.

Alternatively, both coefficients might conceivably be merged into one, this singular value determining 'power' for the purposes of penetration, while its inverse determines how much of the absoption value is deducted.