Dawn of War Maps

A mob of Chaos Space Marines blast away at a Space Marine Listening Post. Units remain exactly perpendicular to the surface they stand on, regardless of how sloped it is. In the case of Heavy Bolters, they'll look like they're firing into the air or the ground, but rest assured they are blasting that LP to bits. The map is flat; it only looks 3D because of an invisible painted height map that determines its shape. Units can shoot through obstacles, the ground and each other with absolutely no ill effects.

The 3D terrain in Dawn of War is created by a painted height map. Characters stand exactly perpendicular to the ground, regardless of what angle it lies at. Some weapons, (e.g. like Heavy Bolters) will also shoot parallel to the ground, regardless of angle; so if you ever see any Heavy Bolter squads standing on a slope firing into the air or the ground, you may rest assured they are in fact blasting the enemy. Its just the way they've been animated: the actual graphics in the game doesn't necessarily show you what's going on inside the game engine itself. Units can shoot through the ground or any solid looking obstacle without restrictions. Squad formations stand in big messy clumps blasting away at each other, through each other. Rubble, destroyed buildings and other set dressing might occasionally block a units path but they're basically just there for looks. Even obstacles are a painted layer: in fact the game engine treats them as a type of cover: Blocking Cover.

This is not a game like Total Annihilation where emergent behaviour decides battles. In an RTS with "realistic" (ho ho) physics simulations, every shell and bullet is worked out on the fly and there's no telling where exactly they might end up. Its actually possible to duck artillery fire in Total Annihilation if you've got the right unit and your wits about you. In DoW, the visual effects and everything you see is largely preordained, like any old two dimensional RTS like StarCraft or Age of Empires. It's one of the "flattest" RTS games around. I think its safe to say that elevation in Dawn of War plays no part in tactics and strategy. (Even StarCraft had rules concerning ground levels!) Being on top of a hill doesn't appear to give a squad any advantage over any squad stuck in a valley. Whether one stands on a mountain top or another is stuck down a mineshaft, if they're both within horizontal range they'll cheerfully blaze away as though on a bowling green. DoW uses the same logic and physics of an old tabletop board game - or more appropriately, its more like a football pitch. Your (team's) tactics, timing and movement pretty much can trump everything in the right time and place.

Cover and Negative Cover

Our Chaos Marines crossing Blood River. The river has negative cover, which means they all suffer a movement penalty and are more susceptible to any ranged enemy fire from its banks. Note the negative cover icons floating above their heads. Cover is determined at a individual level, not at squad level.

Flamers and Burnas negate the effects of Cover. Huddling in a crater won't save your troops from getting singed.

Negative Cover works the other way: units are more exposed than normal to enemy fire. Usually you find Negative Cover in any shallow water, or around the odd Critical Location to make them harder to hold. Its DoW's way of making a choke point. Any unit in Negative cover suffers a 20% movement penalty and is subjected to an extra 10% ranged damage. Close combat damage is unaffected.

Cover bonuses are applied on a unit by unit basis. For the most part they're the same across the board, but some units are special. Space Marine Scouts don't suffer a movement penalty in cover, and neither do any Jump Troops, although they still benefit from the Armour benefits. Hovering vehicles like Landspeeders or most of Eldar's hover tanks don't suffer any movement penalties either, but have slightly lessened armour bonuses. Buildings and structures of all types, including Minefields and Turrets, are immune to the effects of cover.

Necrons are completely unaffected by any kind of Cover.

I suppose if there's a weak spot in DoW, its the shrinking number of Skirmish maps (especially those in the Automatch rotation) that are considered to be "fair". Skirmish maps, especially those used in competitve 1v1 duels, tend to all be perfectly symmetrical, sometimes even down to mirrored crater placement. Starting positions appear in each corner, while and carefully placed obstacles and Strategic Points are arranged in the middle to make life interesting. Smaller, simpler maps are better for rushing, while larger ones with lots of Strategic Points give players the opportunity to tech up and grow quickly. Certainly, the cycle of Automatch maps is limited, since balance has been a contentious issue since the original game was released. Over time, many maps have been dropped for giving one army unfair advantages over another in competitive duels. Dawn of War maps as a general rule have limited slope and offer limited strategic variety compared to other RTS games.