Has it ever been mentioned whether glamours (and other similar illusory magicks, I suppose) have a tactile element to them, or are they simply visual?

If, for example, some patrolling Garlean conscript happened to take a break on one of the glamoured rocks barring entrance to Rhalgr's Reach from the Fringes, would he actually sit on said rock or simply pass through it as though it weren't there?

Or say, with the sylphs, at least two of whom transform themselves into Midlander models. Were someone to bump into Noraxia while she was wandering about in her humanoid form, would they meet contact with the whole body or simply the approximate body mass that a sylph would take up?