Re: 3D coordinate system with Z=Up - rotation directions and starting axis ?

On Sun, 1/26/2025 2:13 AM, R.Wieser wrote:
> Hello all,
> 
> I've used OpenGL to create a basic 3D coordinate system (which works) with 
> Z=Up, X=to the right and Y=into the screen.
> 
> The thing is that I've picked rotation directions and starting axis for 
> those rotations in a "I need it to work, and this does" way. :-|
> 
> Now I'm at a point where I want to make it conform to a/the standard, and 
> have done a few websearches for 3D coodinate systems and their specifics.
> 
> Alas, although I've been able to find pictures of the Y=Up and Z=Up 
> coordinate systems and even a Z=up, rotation=anti-clockwise description 
> (right-hand rule), I could not find anything more - which suprises me to be 
> honest. :-|
> 
> 
> 
> What I'm looking for, for both the Y=up and Z=Up coordinate systems :
> 
> rotation directions for all three axis/planes, as well as starting axis*.
> 
> * Although I've found that for Z=Up the rotation direction is 
> counter-clockwise I do not know at with axis it starts: +X ?  +Y ? 
>  Perhaps -X or -Y ?.  No idea. :-(
> 
> Regards,
> Rudy Wieser
> 
> 

https://www3.ntu.edu.sg/home/ehchua/programming/opengl/CG_BasicsTheory.html

3. Vertices, Primitives, Fragment and Pixels

3.1 3D Graphics Coordinate Systems

    OpenGL adopts the Right-Hand Coordinate System (RHS). In the RHS, the x-axis
    is pointing right, y-axis is pointing up, and z-axis is pointing out of the screen.

    With your right-hand fingers curving from the x-axis towards the y-axis,
    the thumb is pointing at the z-axis. RHS is counter-clockwise (CCW).
    The 3D Cartesian Coordinates is a RHS.

    Some graphics software (such as Microsoft Direct3D) use Left-hand System (LHS),
    where the z-axis is inverted. LHS is clockwise (CW).

    In this article, we shall adopt the RHS and CCW used in OpenGL.

*******

Try it their way and see if it works ?

https://www3.ntu.edu.sg/home/ehchua/programming/opengl/images/Graphics3D_RHS.png

   Paul