# Rotation matrix - pyode and goocanvas

• From: Fionn Ziegler <fionnziegler gmail com>
• To: goocanvas-list gnome org
• Subject: Rotation matrix - pyode and goocanvas
• Date: Fri, 3 Dec 2010 13:51:06 +0100

```Hi,
I'm writing a small game (for adding) using goocanvas and the open
dynamics engine (ODE) or thre python wraper for that.
A already managed a lot but now I've a unsolved problem. Maybe its a
lack of math skills I don't know.
Ho can I spin a (Goocanvas) Ellipse.
>From ODE i get the Rotation
"getRotation()
Get the current orientation of the geom. If the geom is attached to a
body the returned value is the body's orientation.
Returns:
9-tuple"
Is there a way to manipulate directly the object matrix?
in the ODE FAQ is the following explanation:
http://opende.sourceforge.net/wiki/index.php/FAQ#I_have_a_matrix_does_dBodygetRotation_return_ABCDEFGHI_or_ADGBEHCFI_.3F

| A B C |
M =  | D E F |
| G H I |

which is the reverse of what you'd use in OpenGL (which is also column
vector on the right).

So my question is: how can I apply these ODE matrix to the goocanvas?
Or how to change the matrix (like orientation/direction)

Thanks for any help,
Regards,
Fionn

This is the code to set the ellipse position of the ode_body

x2, y2, z2 = body.getPosition()
goo.set_properties(center_y=y2, center_x=x2)

an interesting topic: http://osdir.com/ml/lib.ode/2002-12/msg00176.html
more math stuff:
http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToAngle/index.htm
```

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