projection Onto Plane.

 BBS: Inland Empire Archive
Date: 05-06-92 (23:44)             Number: 149
From: DAVID BLISS                  Refer#: NONE
  To: RICH GELDREICH                Recvd: NO  
Subj: projection Onto Plane.         Conf: (2) Quik_Bas
 >     Lets say we have a four sided plane in 3-D space,
 > like this:

 >     x----x
 >     !    !
 >     !    !
 >     !    !
 >     x----x

 >     Where each "x" has an X,Y, & Z coordinate. The
 > plane could be in any
 > position, not just what you see here.

 >     What I need: The coordinate of a point which is
 > perpendicular to
 > this plane when a line is drawn threw it to the center
 > of the plane. If
 > that isn't hard enough, the point must also be a
 > certain distance from
 > the plane too(such as 64 units or so). I can easily

This is so amazingly simple <g> (no offense of course!).
To find X,Y,Z of the point you said (assuming i understand
you), assuming the plane has four corners 1-4 and X,Y,Z of
these are X1-4 Y1-4 and Z1-4 and the point you need is X5
Y5 Z5,

X5=(x1-x2)+(x3-x4)/2   or whichever corners are on same line
Y5=(y1-y2)+(y3-y4)/2   "    "          "     "   "   "    "

What this does, is find the middle of the left side of the
plane, then the middle of the top side, and then give you a
point 64 units above that point.  very simple geometry <bg>
but then i'm in very advanced math <g>

Hope this helps,

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