I use square grids in my campaign and during my last session I was trying to check how many PCs I could hit with a dragon's breath. Now since this dragon is a large creature I was thinking how many point of origins I have and I could not find a good documentation except that any intersection between squares can be considered as such, which rules out the white area inside the squares, but what if the creature is large or huge?
I tried using common sense: the dragon occupies 4 squares so since he is free to choose in which direction he wants to blow he can surely chose any of the 4 corners right? What about the other 4 non corner intersections? I guess those also make sense, right?
Then what about the central intersection of the 4 squares? Can the cone originate from the center of the dragon? It kinda make sense to me: the dragon tilts his head up and blows more down then forward, so less far, but it gets more adjacent units.
Last crazy thought, what if the dragon tilts its head back? It would be like originating from a corner, but traveling on the opposite direction.