Line of Sight through Freindly/Enemy Units?

Hi

The rules clearly state that, "You cannot charge Units that you cannot see" (5.8 Charges) but I cannot find anything about whether friendly or enemy units block line of sight or not (assuming that the unit trying to 'see' and the 'blocking' unit are on the same level). I am not just thinking of charges but other instances for instance the rule about impetuous troops within 30U of any visible enemy (5.3).

I did find a similar question on the forum from last year - (http://impetus.ativiforum.com/t465-line-of-sight?highlight=line+of+sight) but the answer seemed to contradict the main rules.

Sorry if I have missed it in the main rules but it came up in a game the other evening.
Bye the way the more I play these rules the more I enjoy them but they badly need all the rules in one place (i.e. Impetus 2).

Grateful for some clarification.

Cheers Paul

Units (friendly or enemy) do not block line of sight for purposes of charging and causing impetuous units to lose control etc.. LOS is not the same as visibility. LOS is only effected by terrain.