Explaning linuxcnc implement kinematics of a new robot

thank you so much Andy,
i have a question on another thing, now i have a .STL file for my CNC and i want to implement it to vismach using python code
linuxcnc.org/docs/html/gui/vismach.html
now i can draw some basic shapes like spheres and cylinders etc, even i didn't fully understand the code particularly the function Capture(), however i have another problem when implementing from cad exported as .STL like i said, the problem is that the model doesn't appear like the sphere does, also the orientations or define the rotation or movement of each part relative to each other or even assembling the model will be so impossible as is see it becouse i have to position each part relative to another ....

You can position the parts in the python code prior to assembling the model. But it's easier to have everything in the right place in the CAD model, and have the CAD model on the correct origin part, then import that.

Yes, this idea of assembling the cad model then importing it to python is alot easier but the problem is that how to define the joints so that i can make each joint move by itself?

I wrote the Vismach documentation, and that really is my best attempt at explaining it. Anything I wrote here would just be repeating what I wrote then. Except that I understood it then and have forgotten it since.