Filq wrote:Can you shoot at inf unit that is moving behind another inf unit? In theory, I can always see parts of the models through the gaps of first line unit. No matter how thick and dense would be the first line of the models. Or do I have to be able to see whole base of model I want to shoot? In that case 1st line will cover part of it.
As long as the shooting model can see even the tiniest sliver of the target model, it can fire to full effect. Other models can't affect this, only certain terrain can. Unlike in previous editions, where shooting "though" other units could affect your shooting, in 9th it does not.
Keep in mind that some models, if packed tightly enough, can theoretically block line of sight, but only if they are really packed tightly enough to 100% block it.