[ODE] Understanding Rotation Matrix

Joey Coyle ode at xcoyle.com
Tue Nov 23 18:32:44 MST 2004


I am new to ODE, and new to Matrices, and 3D

I have looked through the documentation, and I can't figure out the 
layout of the rotation matrix.

> These functions set and get the position, rotation, linear and angular 
> velocity of the body. After setting a group of bodies, the outcome of 
> the simulation is undefined if the new configuration is inconsistent 
> with the joints/constraints that are present. When getting, the 
> returned values are pointers to internal data structures, so the 
> vectors are valid until any changes are made to the rigid body system 
> structure. Hmmm. dBodyGetRotation returns a 4x3 rotation matrix.

How is this rotation matrix laid out?

On the web, I find a rotation matrix looks like this

R11    R12   R13
R21   R22    R23
R31   R32   R33

where Row 1 is Right,
Row2 is Up
Row3 is Out.

Why is ODE returning a 4x3 matrix?   And how is the array laid out??


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