(I was going to put this under the Invisible Flashlights topic but I'm interested in actual house rules GMs have come up with for invisibility. I've had some players who LOVE their physical invisibility spells and I had to step in to clarify the subject for my own sanity. )

Booklord's Invisibility House rules
-----------------------------------------

House Rule #1
--------------------------
Physical Invisibility DOES NOT bend light.
Instead Invisibility does two things.

1) It dissapates light being reflected off of or generated ( such as thermographic light generated by body heat ) by the invisible subject. The light still hits the target. It is the reflection of the light that is dissapated.

2) It generates the physical illusion of the light being projected from the exact opposite point of the body where the light hits the target.

Example: Planning a daring raid a group of shadowrunners, realize that though they can sneak into the facility undetected once they'll once steal the loot they'll set off an alert and they'll have to run for through the outer perimeter past two laser turrets which will be operating independently from the net. As part of their plan they cast a physical invisibility spell onto a sheet of high density metal and place that sheet in front of the laser turret. The run goes as planned and as the runners race out of the facility to the waiting getaway vehicle, the turret opens fire. But the turret's laser strike the invisible sheets of metal instead. Then the improved invisibility spell creates the physical illusion of the laser light striking the characters. The characters are completely unharmed by this laser light being generated by the invisibility spell as the real laser blasts are striking the sheet metal and leaving behind (sight unseen) some rather nasty scorch marks.

This houserule was brought to you by players who really thought I'd let them walk through a high-security laser grid ( the damaging kind ) simply because they were invisible.

Under this rule an invisible flashlight would not generate light unless the intensity of the light exceeded the strength of the invisibility spell. Likewise thermographic light generated by intense heat might also penetrate the invisibility spell. ( Careful with that blowtorch buddy! ) Any light such as a laser capable of doing damage would automatically pierce the invisibity spell.

House Rule #2
----------------------------
Further House rule: As physical Invisibility affects the light hitting the character and being generated by the character it cannot be resisted by other characters. ( Physical Invisibility affects the invisible guy. Mana Invisibility affects everyone else ) At best someone viewing an invisible character can try to detect the difference between the physical illusion light and real light and get a rough idea of where the invisible person is. Technology capable of analyzing light would also be helpful in this regard and may be capable of detecting a physically invisible character. A weak physical invisibility spell would make you like the Predator. Yeah you're invisible but anyone looking closely will be able to make out that someone is there. A strong invisiblity spell would make you nearly undetectable. A magician if he is capable of detecting where an invisible person is can target an invisible character with a spell. ( Though some target modifiers would still apply ) It should be noted that the less light there is the less work the invisibilty spell has to do and the more effective it becomes. So attempts to detect a physcially invisible character would be affected by visibility modifiers.

Note: Invisibility technology would work in a similar fashion with an invisibility suit absorbing light and then projecting the exact same amount and type of light out the opposite side of the suit. Can you imagine how hideously expensive that would be with today's technology? But it is something that may be possible using Shadowrun's nanotechnology to construct the millions of micro light analyzers, absorbers and transmitters necessary to similulate invisibility. Nanotech is good when it comes to freakishly mind-boggling repetitive tasks.

Further Note: I haven't decided what would happen if a magician tried to target a character standing on the other side of an invisible wall being that he's not actually seeing the character but instead seeing the physical illusion of the character generated by the invisible wall. Thankfully its never come up. But I'm thinking the answer would be no. The Magician can't actually see the individual so he can't target them. It'd be like the magician was trying to target a life-like hologram of the target. It wouldn't work though the magician may not be immediately aware to why.

TBH I'd be inclined to just rule that the photons pass right through the mage (or whatever has been targeted by the spell). How? It's magic!

The force of the spell would, in this situation, govern the transparency of the target.

How this would work with regards to an invisible item being a light source, I'm not entirely sure, although probably the light energy being generated by the torch is unaffected. Hence an invisible paraffin lamp would be visible as a floating flame, the handle, case and fuel reservoir being invisible. The hand torch mentioned would be invisible except for anything caught in the beam, which would see the light from the bulb.

It's dirty, and it doesn't make physical sense, but so what?

It seems to me that if Invisibility bent light in such a way as to make the subject immune to laser damage and the effects of flash grenades, it would also make the subject blind. The sense of sight is a result of light hitting the various parts of the eye.

My advice is to say that Invisibility does what it says it does, no more, no less. If anyway asks why, wave yours hands over your head and yell, "It's magic!"

If anybody asks how, use the same procedure as for why.

I'm just toying with the idea of making Invis/ImpInvis function like ruth cloaking, with successes adding extra whatevers until you get to the same threshold. I think it's +4, now.

I like the first house rule you used.

I like this rule because it retains all the canon mechanics (the resistance roll) only deviating in terms of fluff and unspecified situations

The on thing you didn’t clarify was the situation of illumination threw an invisible object (invisible door between a lit room and a dark room, invisible cover on a torch)

Edward