[Bf-python] quat multiplication

[models at paposo.com]

They look that way but check this out. I put the formulas into an excel
spreadsheet.  I think that blender's coordinates are rotated or something:

----- Original Message -----
From: "Willian Padovani Germano" <wgermano at ig.com.br>
To: <bf-python at blender.org>
Sent: Thursday, November 27, 2003 7:00 PM
Subject: Re: [Bf-python] quat multiplication


> Hi,
>
> >  t0=   q1[0]*q2[0]-q1[1]*q2[1]-q1[2]*q2[2]-q1[3]*q2[3];
> >  t1=   q1[0]*q2[1]+q1[1]*q2[0]+q1[2]*q2[3]-q1[3]*q2[2];
> >  t2=   q1[0]*q2[2]+q1[2]*q2[0]+q1[3]*q2[1]-q1[1]*q2[3];
> >  q[3]= q1[0]*q2[3]+q1[3]*q2[0]+q1[1]*q2[2]-q1[2]*q2[1];
> >  q[0]=t0;
> >  q[1]=t1;
> >  q[2]=t2;
>
> >   x = qw * q.x + qx * q.w + qy * q.z - qz * q.y;
> >   y = qw * q.y - qx * q.z + qy * q.w + qz * q.x;
> >   z = qw * q.z + qx * q.y - qy * q.x + qz * q.w;
> >   w = qw * q.w - qx * q.x - qy * q.y - qz * q.z;
>
> > when you multiply the quats, blender gives:
> > q3 = [-4,4,4,4] (w,z,y,x)
> > and cal3d gives:
> > q3 = [4,4,4,-4] (x,y,z,w)
>
> No, look again at the two sets of multiplications, comparing for example
> t1 in the first with x in the second.  Blender stores quats as
> (w,x,y,z) -- the real part is at index 0, that's the only difference.
>
> --
> Willian, wgermano at ig.com.br
>
> _______________________________________________
> Bf-python mailing list
> Bf-python at blender.org
> http://www.blender.org/mailman/listinfo/bf-python
>
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: qMult.xls
Type: application/vnd.ms-excel
Size: 14848 bytes
Desc: not available
URL: <http://lists.blender.org/pipermail/bf-python/attachments/20031127/11341c2f/attachment.xls>