Cinema 4D Python: Control Besier Spline With Python Tag.py

"""
How to connect bezier spline points to objects 
and control tangents with Python Tag in Cinema 4D.

View tutorial and get project files here
https://mikeudin.net/?p=7503


Author : Mike Udin
Web-site : mikeudin.net
Tag : Python

"""

import c4d


def main():
    
    spline = op.GetObject()

    start = spline[c4d.ID_USERDATA,2]
    end = spline[c4d.ID_USERDATA,3]

    if (not start) or (not end):
        return
    
    use_global_tang = spline[c4d.ID_USERDATA,5]
    global_tang = spline[c4d.ID_USERDATA,6]

    start_tang = start[c4d.ID_USERDATA,1]
    end_tang = end[c4d.ID_USERDATA,1]

    start_mx = start.GetMg()
    end_mx = end.GetMg()
    smx = spline.GetMg()

    if use_global_tang:
        start_tang = end_tang = global_tang

    start_tang = (start_tang * start_mx) - start_mx.off
    end_tang = (end_tang * end_mx) - end_mx.off

    spline.SetPoint(0,start_mx.off * ~smx)
    spline.SetTangent(0,start_tang * -1,start_tang)
    

    spline.SetPoint(1,end_mx.off * ~smx)
    spline.SetTangent(1,end_tang,end_tang * -1)

    spline.Message(c4d.MSG_UPDATE)