Forum: Ruby Matrix class for ruby?

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A2cf2d2cd16c5030bff8c123b843fd89?d=identicon&s=25 seepee (Guest)
on 2006-12-21 13:42
(Received via mailing list)
Does anyone know of a functional Matrix math class for ruby that could
multiply, add and substract 3x2 or larger matrices.

The matrix.rb that is in Ruby API cannot multiply anything larger than
2x2
matrices, which makes it useless for 2D or 3D graphics (for instance).

SP
3da82a61d5fbd74242cc6f671a5a32e4?d=identicon&s=25 Nicolas Desprès (Guest)
on 2006-12-21 13:50
(Received via mailing list)
On 12/21/06, seepee <see@pee.org> wrote:
> Does anyone know of a functional Matrix math class for ruby that could
> multiply, add and substract 3x2 or larger matrices.
>
> The matrix.rb that is in Ruby API cannot multiply anything larger than 2x2
> matrices, which makes it useless for 2D or 3D graphics (for instance).
>

Are you sure?

$ irb
irb(main):001:0> Matrix[[1,2,3],[1,2,3],[1,2,3]] *
Matrix[[1,2,3],[1,2,3],[1,2,3]]
=> Matrix[[6, 12, 18], [6, 12, 18], [6, 12, 18]]
irb(main):002:0> VERSION
=> 1.8.4
$
Ea24c17719a975fb38c107a60f4b3802?d=identicon&s=25 Vincent Fourmond (Guest)
on 2006-12-21 14:26
(Received via mailing list)
seepee wrote:
> Does anyone know of a functional Matrix math class for ruby that could
> multiply, add and substract 3x2 or larger matrices.
>
> The matrix.rb that is in Ruby API cannot multiply anything larger than 2x2
> matrices, which makes it useless for 2D or 3D graphics (for instance).

  OK, I understand now: you want graphical transformations. They are
*not* real matrices, but the combination of a real matrix and a
translation vector. So you need special rules to combine them (although
for additions and substractions, standard matrix multiplications should
work). I don't know any package doing that in Ruby -- but if you
consider writing one, that would definitely be an interesting addition.

  Cheers !

	Vince
822f398dd085da080bbe6c7e7b53d3ba?d=identicon&s=25 Dan Uznanski (Guest)
on 2006-12-21 16:30
(Received via mailing list)
On Dec 21, 2006, at 6:24 AM, Vincent Fourmond wrote:

> translation vector. So you need special rules to combine them (although
> for additions and substractions, standard matrix multiplications should
> work). I don't know any package doing that in Ruby -- but if you
> consider writing one, that would definitely be an interesting addition.
>
An RST matrix has an implicit 0 0 0 1 row along the bottom.  Nothing
more complicated than that.

Actually when dealing with projection matrices, this 'implicit' bottom
row gets used to define the perspective value of the camera.

That said, matrix.rb is very shoddy - it's missing several important
vector operations (like, oh, -Vector and Vector/Numeric), and it uses
Vector*Matrix instead of the correct Matrix*Vector.

Dan
3bb23e7770680ea44a2d79e6d10daaed?d=identicon&s=25 M. Edward (Ed) Borasky (Guest)
on 2006-12-21 16:54
(Received via mailing list)
Dan Uznanski wrote:
>>
> Actually when dealing with projection matrices, this 'implicit' bottom
> row gets used to define the perspective value of the camera.
>
> That said, matrix.rb is very shoddy - it's missing several important
> vector operations (like, oh, -Vector and Vector/Numeric), and it uses
> Vector*Matrix instead of the correct Matrix*Vector.
>
> Dan
>
>
>
I wouldn't call it "shoddy". My biggest complaint with Matrix is that a
Matrix is immutable -- if you want to set elements, you have to do so in
an Array and then create a new Matrix from the Array.

The whole rational / complex / matrix / mathn collection looks to me
like an attempt to provide "high-school algebra" constructs in Ruby that
work the way you'd expect them to work. For example, you can get the
*exact* inverse of a non-singular matrix with rational elements, and I
suppose, though I haven't tried it, the same thing for a non-singular
matrix with complex rational elements. For *small* one-off calculations
and calculations where high speed isn't required, they do just that.

However, if what you want to do is, say, lots of graphical
transformations at high speed using floating point arithmetic, like you
might in a video game, you want NArray.

--
M. Edward (Ed) Borasky, FBG, AB, PTA, PGS, MS, MNLP, NST, ACMC(P)
http://borasky-research.blogspot.com/

If God had meant for carrots to be eaten cooked, He would have given
rabbits fire.
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