damped-track-aim

Damped Track Aim

A runnable example that aims twelve brass spikes at an ember core with Object.constraints.new('DAMPED_TRACK') — the data-API path, not bpy.ops.object.constraint_add (which needs an active object and fails in headless loops). Damped Track is the twist-stable aim constraint: it points one local axis at a target without the roll fights Track To is known for.

What it witnesses: every spike carries exactly one unmuted DAMPED_TRACK bound to the core on TRACK_Z. After a depsgraph update, each evaluated local +Z aligns with the world vector toward the core (dot ≥ 0.998 ≈ 3.6°). A missing constraint, a muted one, a TRACK_TO stand-in, or a flipped axis fails the check.

Framing deviation

Radiating composition — the twelve spikes read as converging on the core from beyond the frame, so their tails bleed past the left, right, and bottom edges by design (measured fill 1.000x/0.917y with edge touch on three sides). If wired to examples/gallery_framing.py, call it with deviation="radiating composition; spikes read as extending past frame".

Run

# Cheap correctness check (no render) — the CI check:
blender --background --python damped_track_aim.py --

# Also render a still (EEVEE on a GPU host; use --engine cycles on GPU-less hosts):
blender --background --python damped_track_aim.py -- --output aim.png
blender --background --python damped_track_aim.py -- --output aim.png --engine cycles

It exits non-zero on failure (wrong constraint type/target/axis, or evaluated aim outside the angular epsilon). The blender-smoke workflow runs the check on Blender 4.5 LTS and 5.1.