[ODE] matrix multiplication

Wed Mar 12 09:28:01 2003

For what it's worth the following great book has a
simplified explanation of this and other matrix
tecniques. While not a "Game Math for Dummies" it does
explain matrix math simply and from a game programmer
point of view instead of the usual matrix explanations
which are geared toward mathematicians.

http://www.amazon.com/exec/obidos/tg/detail/-/1556229119/qid=1047486129/sr=1-1/ref=sr_1_1/103-4731875-8322238?v=glance&s=books

 So if you stupidly majored in something like History
realized Law School was a complete waste of time and
switched careers into game programming this book is
for you.

john

--- Henri Hakl <henri@cs.sun.ac.za> wrote:
> It's quite simple, consider:
> 
> A = B * C
> 
> if B is a 5 x 3 matrix and C is a 3 x 4 matrix then
> A will be a 5 x 4
> matrix, (B's second and C's first parameter HAVE to
> be the same, the
> resultant matrix has dimensions according to B's
> first and C's second
> parameter), accordingly you'd use:
> 
> dMultiply0(A, B, C, 5, 3, 4)
> 
> 
> ----- Original Message -----
> From: "Fig TaTam" <fig_tatam@hotmail.com>
> To: <ODE@q12.org>
> Sent: Wednesday, March 12, 2003 12:32 PM
> Subject: [ODE] matrix multiplication
> 
> 
> > ok, I figured out how to do that rotation I
> wanted, so don't respond to
> > topic "Re: [ODE] rotation matrix from normalized
> vector?"
> >
> > But now I have a question about matrix
> multiplication. Ode has a function
> > for that described as:
> >
> > /* matrix multiplication. all matrices are stored
> in standard row format.
> > * the digit refers to the argument that is
> transposed:
> > *   0:   A = B  * C   (sizes: A:p*r B:p*q C:q*r)
> > *   1:   A = B' * C   (sizes: A:p*r B:q*p C:q*r)
> > *   2:   A = B  * C'  (sizes: A:p*r B:p*q C:r*q)
> > * case 1,2 are equivalent to saying that the
> operation is A=B*C but
> > * B or C are stored in standard column format.
> > */
> >
> > void dMultiply0 (dReal *A, const dReal *B, const
> dReal *C, int p,int q,int
> > r);
> >
> > What I don't understand is what I'm supposed to
> pass as 'p', 'q', and 'r'.
> > Anyone know?
> >
> >
>
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