This came up in game tonight. Thunderwave is a spell with Range: Self (15-foot cube). The description reads:
A wave of thunderous force sweeps out from you. Each creature in a 15-foot cube originating from you…
Players Handbook, 282-283
Does the area of effect center on the caster (extending 7.5 feet in each direction), or does it begin from the caster, and extend in the direction desired (for a full 15 feet)?