Lately I have worked a lot with alembic files that have point level animated geometry and once I had to attach objects to that PLA geometry. I figured out a couple different ways to do this (e.g. MoGraph Cloner or Contraint Tag) but my favorite solution is to use Xpresso and Python.

In this setup I’m taking three points from selected polygon. Then I’m creating vectors v1 and v2 from those points’ positions. Then vectors are used to generate orthogonal axes by using cross product.

import c4d
import math

def main():
    global Matrix

    v1 = Point1 - Point0 # Generate first vector from two point positions
    v2 = Point2 - Point0 # Generate second vector from two point positions

    m = c4d.Matrix() # Initialize a matrix
    m.v1 = v1.GetNormalized()
    m.v3 = v1.Cross(v2).GetNormalized()
    m.v2 = m.v3.Cross(v1).GetNormalized()
    m.off = Position # Set position

    Matrix = m # Output

ar_xpresso_align_object_to_pla_polygon.c4d