FunkAztec wrote:So just to clarify, will a model/unit benefit from light/dense cover if
LOS passes even 1mm through something like an obscuring piece of terrain that also has a light/dense rule attached?
Page 262 (Terrain Traits) says:
Dense Cover
If this terrain feature is at least 3" in height, then subtract 1 from the hit roll when resolving an attack with a ranged weapon unless you can draw straight lines, 1mm in thickness, to every part of at least one model's base (or hull) in the target unit from a single point on the attacking model's base (or hull) without any of those lines passing over or through any part of any terrain feature with this trait...
So basically, if the attacker has a clear shot against at least one model in the target unit, you can ignore the to-hit penalty from dense cover.
Light cover (the bonus to your armor save) kicks in when a model "is receiving the benefits of cover." Whether or not you receive the benefits of cover is based on the Terrain Categories section on
pg. 260. But the short answer is that you generally only benefit from light cover when you're standing on the footprint of the terrain. Example: Ruins and woods are both listed as examples of "Area Terrain" (that's a terrain category). Area terrain says...
Infantry, swarm, and beast models receive the benefits of Area Terrain features while they are within it.
So if you're shooting at an enemy squad with 3 guys in a ruin and 7 guys outside of it, those three guys would benefit from light cover (+1 to their saves), but the other 7 guys would not. This is why you'll see players rolling separately for models in and out of cover; usually rolling for guys in cover first because they're more likely to tank a few extra shots before dying.
Honestly, I really like the bones of the 9th edition terrain rules. I haven't run into a lot of ambiguity with them, and I've yet to have a debate over whether or not someone receives such and such benefit.