Drive a VizGroup transform from a BasisN3 Motor

Keywords: BasisN3 · Motor · VizGroup · Transform · scene graph · animation

Builds a motor in the BasisN3 (N3) algebra and uses it to drive a VizGroup: the initial placement is set from the motor's multivector, then a fresh motor is applied (composed) each frame to keep the group spinning. set_transform and apply_transform accept the same inputs — a Transform, an MV, or a GA operator (Rotor/GeneralRotor/Motor/Translator/Dilator).

Run

uv run python py/examples/viz/scenes/motor_group_transform.py

Source

viz/scenes/motor_group_transform.py

Code

# SPDX-License-Identifier: Apache-2.0
# Copyright 2021 Christian Perwass

"""motor_group_transform.py — Drive a VizGroup transform from a BasisN3 Motor.

Builds a motor in the BasisN3 (N3) algebra and uses it to drive a ``VizGroup``:
the initial placement is *set* from the motor's multivector, then a fresh motor
is *applied* (composed) each frame to keep the group spinning. ``set_transform``
and ``apply_transform`` accept the same inputs — a ``Transform``, an ``MV``, or
a GA operator (``Rotor``/``GeneralRotor``/``Motor``/``Translator``/``Dilator``).

Run with:  uv run python py/examples/viz/scenes/motor_group_transform.py

Keywords: BasisN3, Motor, VizGroup, Transform, scene graph, animation
"""

import math

from pytanga import MV
from pytanga.basis import BasisN3
from pytanga.geometry import Direction, Geometry, Line, Motor, Point, Rotor, Translator
from pytanga.viz import LineStyle, PointStyle, Visualizer, VizGroup

N3 = BasisN3()
geo = Geometry(N3)


def motor_mv(angle: float) -> MV:
    """A BasisN3 (N3) motor as a multivector.

    Rotate about +Z while translating in the XY plane, built through the
    BasisN3 algebra and returned as its ``MV`` — one of the inputs that both
    ``set_transform`` and ``apply_transform`` accept.
    """
    return geo.create(
        Motor(
            Rotor(angle, Direction(0, 0, 1)),
            Translator(0.05 * Direction(math.sin(angle), math.cos(angle), 0)),
        )
    )


viz = Visualizer(title="Tanga — Motor-driven VizGroup transform")
viz.show()

# Initialize the group's transform from a BasisN3 motor (set = replace).
body = VizGroup("spinner")
body_ref = viz.new(body)
body_ref.set_transform(motor_mv(0.0))  # initial placement

# Children live in the group's local frame, so spinning the group spins them too.
body_ref.new(
    Point(0, 0, 0), color="#ffaa00", label="pivot", style=PointStyle(size=0.10)
)
body_ref.new(
    Line.from_points(Point(0, 0, 0), Point(1.5, 0, 0)),
    color="#ff5555",
    label="rod",
    style=LineStyle(thickness=3.0),
)
body_ref.new(
    Point(1.5, 0, 0), color="#44ff44", label="tip", style=PointStyle(size=0.12)
)

viz.flush()

print("A rod + tip group spins, driven by a BasisN3 Motor.")
print("set_transform() sets the initial placement; apply_transform() composes")
print("each frame. Close the browser window or press Ctrl+C to exit.")

print("Starting animation...", flush=True)
speed = 1.2  # rad/s
fps = 30  # frames per second
delta_motor = motor_mv(speed / fps)  # incremental motor per second
for dt in viz.animate(fps=fps):
    # Compose an incremental motor onto the group's current transform.
    body_ref.apply_transform(delta_motor)
    viz.flush()

print("Animation stopped.")
viz.stop_server()