I've had different kinds of visual effects when smoking alot of weed or hash, like shimmery edges on things and an effect like things were sort of under water. Also I have had trouble judging distance, a sense that things look much further away than they really are. I've had an illusion that even though I am walking toward something, it never gets any closer. But I would not say I have had a full-on hallucination, not like what you might experience with other substances that we do not talk about here.