🚀 go-pugleaf

In article <312028C1.C1F@nmsu.edu> jshagam@nmsu.edu "Quantum Porcupine" writes:

> Paul Rowntree wrote:
> > 
> > Sorry, but I must take offense here.  A point in Cartesian space has three
> > aspects [X,Y,Z].  A vector requires a direction, and depending on how sticky
>  you
> > are, probably a length.  This implies 6 independent aspects.  Result;  A plane> > requires 3 points.  Always.

What ?!  All Vectors have length.  Something with no length but direction is
just a couple of angles, sometimes usefully referred to by a unit vector.
(Length 1)

> You're wrong. A vector is any quantity with any given number of dimensions. The
> number 5 is a vector, called a scalar.  The vector [x,y,z] can refer to a
>  position
> vector (point) or direction vector.
> 
> I suggest you take some math courses before you try to explain such basic
>  concepts.

Yeah.  And also that point about you need 3 points to define a plane ?

Well, if you only have points then you need a 3 points *which are not
collinear* -- you can have an infinite number of points in a line and you
will never define just one plane.

A much easier, and more useful result is to cross vectors between those points
and get yourself a normal to that plane, then get its distance from the origin

iirc the normal vecotr is used for shading.
-- 
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