These are only my interpretations...
Let's never forget Power Perception, Attunement, Situational Awareness: Hide and Seek for the one visible, or even a high Presence stat of the one invisible.
Mediums the world over often state "I sense a presence." Unless you can quiet your mind, by spell or meditation, you still have a high Presence, IMHO. This
could be a penalty to any chance to be hidden...
Some people are more intuitive than others... High Intuition stat should give a nice bonus for detecting "presences."
Many casters and the more powerful creatures (in my experience) have some form of Power Perception. This always kept our magic to the minimum required... The last thing you want is to attract the attention of something that the party isn't tough/smart enough to handle!
MDC, this sounds a
bit similar to what you're talking about.
So if a tree, wall, or something is in the way of the observer , he will more probability to detect the invisible one. Vince, I agree... and 10' sounds like the distance that we are talking about. At 10' the bonus is +20 (pretty high..).That's if they are stationary. Now scale that however you like... maybe at 1' the bonus is +50 (or 30, 40, 90 whatever number you like). Once you have a scale, then find the +/- at any distance. It could be that at 20' the bonus is still +10... Whatever your scale.
The suggested rule, to me, reads that you don't "break" the spell. You are noticed if you roll a "Falls" OR "Falls Down" on the MM table. If you roll either of these two, you're seen; not invisible any more.
If you "attack" OR are "struck by a violent blow", then you're visible.
You may, however, perform any maneuver you like while invisible! IMO, these are implied by the different penalties for different MM.
You may move faster than a walking pace..(I never took this to be anything more than "move." Any way you move- on a boat, riding a shark, on a kite, running, flying... moving doesn't "break the spell."
Moving invisibly, does (!) make it much easier to see you. The modifier is based on the difficulty of your maneuver. "If" they can now see you... then you're not invisible.
Nders,
I found that in the back of the "Of Mentalism" book; first thing I grabbed.
Another way to control Invisibility, or in fact any target affecting utility spell would be something similar. Perhaps the inherent use of magic on life can have severe stressful physical effects for anything longer then short term. Vroomfrogle, This reminds me of Mythus' magick system. It's basically radiation that is everywhere in many forms. Many people can control Heka, Baraka, Vril, Magic, but the more you do, the less likely you are going to have children. So a kingdom that has tons of magic, won't have many casters or even soldiers! IIRC..