[cad-linux] Re: database access methods

On 2003.05.16 12:06 Roland Krause wrote:

> >
> > viewer.  Does anyone know a simple routine to convert a vector to
> > OpenGL rotation angles ?  You can not use simple force resolution
> > routines.
> 
> Do you mean a virtual trackball that allows you to rotate the scene or
> a camera? I have both, let me know what you need. They are from the
> net, if you google for virtual trackball you will find them.
> 
> Roland
> 
> 

Not quite.  An example should help.  Suppose your model is centered on 
a global orthoginal right handed coordinate system.  You are at a 
arbitrary distance far enough away to see the entire model.

If you are looking down the Z-axis at the X-Y Plane.  The orientation 
unit vector would be: (0i + 0j + 1k)

Now let say you want to rotate the coordinate system so you are looking 
down the X-axis at the Y-Z plane.
The new orientation vector is (1i + 0j + 0k).  This requires a 90 
degree rotation about the Y axis in OpenGL.

Now it is easy to write a simple if-else code block for the six major 
faces.  What I am looking for is a general routine to handle any 
arbitrary vector.  An example would be a isometric view obtained by a 
30 degree rotation about the X-axis, then another 30 degree rotation 
about the Y-axis.

Like I said in my previous post, you can't simply extend the force 
resolution routines.

thanks for your help.

cheers,
Jim Parker

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