Affine transforms - matrix algebra

Pavel Safrata pavel.safrata at
Tue Aug 14 00:42:00 PDT 2012

Ok, you've convinced me.

On 14.8.2012 2:03, Jim Graham wrote:
> On 8/13/2012 12:33 PM, Pedro Duque Vieira wrote:
>>>>           // Gets distance from the origin (lenght of a vector)
>>>> I'd prefer getMagnitude(), this way it's obvious your getting the 
>>>> lenght
>>>> of a vector
>>>> I'm not sure, magnitude of a point is similar nonsense to length of a
>>>> point and I guess users would search for the word "length" first. Does
>>>> anyone else have an opinion on this?
>>>   You're already doing things that make no sense for a Point3D, like
>>> adding two points, so it's pretty obvious that this is being used to
>>> represent Points and Vectors so this shouldn't be hidden from the 
>>> user to
>>> prevent further confusion.
>>> I think this should really also be stated on the javadoc of Point3D.
>>> Yes, it will be stated. I'm just not sure why 'magnitude' is better 
>>> then
>>> 'length'..
>> Personally I think it's better because magnitude is mostly applied to
>> vectors so one would immediately infer that he's getting the lenght of a
>> vector. Lenght would also be fine by me though.
> I also suggested magnitude, but I'm also not married to it.
> Some other reasons:
> - vectors are often defined as having "direction and magnitude" 
> (though we don't have a "getDirection" method)
> - normalization is usually specified as dividing by magnitude
> - length is for something with 2 ends, but a point just has one end. 
> We'd have to define it as having an implicit "other end", like "length 
> to the origin".  Magnitude is less colloquially limited that way, 
> though by often being associated with the implicit 'to the origin" 
> that we could just as easily document our way around - but it seems 
> more natural with the term magnitude. Also, consider that an absolute 
> value of a number is often called its "magnitude" with its implicit 
> "direction" (left or right of zero on the number line) discarded.
> I'm OK with either term, though...
>             ...jim

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