IanB said:It isn't a question of looks; fish and some other aquatic animals actually detect the movements of water with a special sensory organ (usually called the lateral organ.) It isn't sonar - that is something else entirely.
In game terms I guess the lateral sense would probably be closest to tremorsense, although it shouldn't be that powerful.
RigaMortus2 said:I interpret "interact with" in that you are doing something to directly try to affect the illusion. More often than not, this is done by attempting to attack it, cast a spell on it, or touch it in some way (or try and walk through it). I allow the caster to manipulate the illusion in such a way that if the illusion were to interact with an actual object, it looks like it is doing exactly that (assuming it is within the area of the illusion).
werk said:I think 'interacted with' means any time that the illusion would need to respond to stimulus, which it is unable to do, or the world should react to it.
Aristeas said:In that case, under what circumstances can one disbelieve a Ghost Sound? Say, the illusion of a harp being played somewhere in the distance. The illusion doesn't have a location or a visible manifestation, so there doesn't seem to be any way to interact with it in that sense. Maybe you get a save if you try to follow the sound back to its source and there isn't a harp there?
Mistwell said:I agree. When a living thing does something to move an object (like an arrow or a sword) into the illusion, or touches it, then that living thing has interacted and gets a save. When an inanimate object that was not moved at the illusion by the opponant in question touches the illusion, the illsion should be maintained as if it properly interacts with the inanimate object.
Otherwise you get into all sorts of wacky decisions like "did a leaf fall onto the illusion" and "does the wind kick up dirt particles onto the illusion" and "does the laps of waves found in the ocean interact with the illusion". Nature, on it's own, doesn't give an opponant a save just because it happens to interact with the illusion. Creatures who cause such things to happen do get a save however.