Line of sight

Do intervening troops interupt line of sight? I would assume they do.
I am thinking about whether impetuous troops have to advance if there are friendly troops between them and the enemy.
Also where would the "line" be taken from? As per the firing range rules?

Talking of impetuous advance, is it correct that they will no longer advance through friendly troops under the advance rule that involuntary forward penatration is no longer allowed?

Thanks
Philip

line of sight is blocked by troops only for firing purposes, not for charging purpose.

Impetuous troop now interepenetrate as other troops, so an Impetuous CP can interpenetrate a S/FL/CL/T but not a FP or a CM or another CP.