Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 7/1/84; site wuphys.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!mgnetp!we53!busch!wuphys!mike
From: mike@wuphys.UUCP (Mike Jones)
Newsgroups: net.games.frp
Subject: Re: fizicks in d&d
Message-ID: <274@wuphys.UUCP>
Date: Fri, 3-May-85 14:25:57 EDT
Article-I.D.: wuphys.274
Posted: Fri May  3 14:25:57 1985
Date-Received: Sat, 4-May-85 02:24:14 EDT
References: <5047@ukc.UUCP> <456@alberta.UUCP> <905@ttds.UUCP>
Organization: Physics Dept., Washington Univ. in St. Louis
Lines: 31

You want fizics, you got it.  I use invisability as an actual bending
(more like light piping) of the light around the invisible object (or
person).  This avoids making invisability a mental attack of the "you
don't see me" type.  The reason I don't like this is that most such
mental influences have saving throws.  Invisability dosn't have a
saving throw, so it isn't like that. (Clerical sanctuary is exactly
like that, and it does have a saving throw).

The objection is that if all the light is bent around the person then
the person can't see.  The key word is all.  How much light do we need
to see?  From my handy Physics Vade Mecum (handbook) we find that
unobscured sunlight is ~10^5 lux (lm m^-2).  A quarter moon at 30
degrees above the horizon (still adequate visability) is about 10^-2
lux.  So the human (not to mention elven or dwarf) eye is capable of
seeing over a range of 10 million in ilumination. So all we need to
allow is an inefficiency of 1 part in 10 million and the person inside
can see.  We can do better than that if we need to.  One in 10 million
is allowing a hole in the invisability the size of the pupil (all the
rest can be 100.0000% effiecient), since we are bending light anyway,
its perfectly reasonable to focus light in from a slightly larger area,
so all we need to see is a patch of perhaps a few square cm which is
99.9999999% effiencent and we can see fine (in full daylight).  This
has to be scaled for lower light, but in full darkness invisability
dosen't have to work very hard anyway.  The detect invisable chance at
high levels is based on slight ineffencies which mean the exact
direction of bending is not perfect or perhaps diffraction effects at
the invisability/ normal space interface.  Sorry this got so long
winded.

Mike Jones Physics Dept. Washington University St. Louis
ihnp4!wuphys!mike