JRRNeiklot said:
That's been a problem in every edition of D&D. I hate the way mages can throw fireballs around with that manner of exaction. It's much like a soldier lobbing a grenade so that it blows the guy up trying to stab his buddy with a bayonet, yet leaving his buddy completely unharmed.
I recently put together some house rules for this that minimize the need for scatter diagrams and to hit rolls against hexes so I thought others might find them handy:
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There are two "hitting your friends" situations that I'll cover here.
The normal D&D rules go with simplicity here, but I've noticed that everyone (my players at least) naturally thinks that firing into tight quarters is dangerous, and tend to be surprised when they discover that the core rules don't make doing so very risky.
Firing Into Melee
Firing a ranged attack into melee already generates a -4 penalty on your attack check.
We'll also add that if you fire into melee such that you suffer the -4 penalty, and roll a natural 1 on your attack check, then your target can choose one adjacent opponent (someone within 5 feet) and force you to make an attack check against them -- this works with all the same bonuses and so on, but no -4 for cover (since this guy IS the cover).
Fireballs In Tight Quarters
If you are caught in an area effect attack and succeed at your saving throw with a natural 20, then you can force one creature who is adjacent to you and outside the area of effect to also save against that attack just as if they were in the area of effect.
Explanation: Explosions and area effect attacks are allowed to be dropped onto the map with extreme precision -- where they might affect a crowd of bad guys but not hit any of the crowd of allies standing right next to those bad guys.
Rather than require a clunky targeting check and add yet more die rolls to the process, the above rule creates a sort of fringe, where lucky targets can share the pain with an enemy that is close to them.