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Christian Svensson 8201f9a954 docs: a flow-past gallery clip and solved still

Add the start-up-transient clip and a solved still of the flow-past sample to
the examples gallery: air flowing past the L-bracket, the wake forming behind
the upright and the drag settling over the 16 s run (it does not shed; that
needs a finer grid or a collision operator stable near the lattice's stability
limit, #557).

tools/flow-clip/make.py regenerates them: it drives the desktop app over the
control channel, solves the lattice Boltzmann step with a dense frame output,
renders the model-only viewport at each frame with a fixed legend clamp
(results.frame then ui.render), and encodes an MP4 and a GIF with ffmpeg, each
frame captioned with the elapsed flow time. The geometry is the sample's own
upright-bracket recipe; nothing comes from a commercial product.

Part of #164.

2026-10-18 10:15:45 -04:00

make.py

docs: a flow-past gallery clip and solved still

2026-10-18 10:15:45 -04:00

README.md

docs: a flow-past gallery clip and solved still

2026-10-18 10:15:45 -04:00

README.md

Flow-past clip

make.py regenerates the gallery clip and still of the flow-past sample (docs/examples.md): docs/media/examples/flow-past-transient.mp4 (the start-up transient of air flowing past the L-bracket, from the uniform 25 mm/s initial field to the settled wake) and docs/media/examples/flow-past-flow.png (a clean iso render of the settled flow).

python3 tools/flow-clip/make.py                   # build, run, encode into docs/media/examples
python3 tools/flow-clip/make.py --no-build        # with the release binaries already built
python3 tools/flow-clip/make.py --frames /tmp/f   # also keep the rendered pictures
python3 tools/flow-clip/make.py --gif             # also write a GIF (not committed; larger)

Needs Python 3 (standard library only), a display for the FieldCraft window (the pictures are drawn offscreen with ui.render, so a locked or virtual display is fine — on a headless machine run it under xvfb-run), and ffmpeg with libx264 on the PATH (or FFMPEG). It honours CARGO_TARGET_DIR; set FIELDCRAFT_GPU=software for a software renderer.

What it does:

Builds fieldcraft and fieldcraft-cli (release) and starts the app with --control PORT.
Opens the flow-past sample and, so the transient plays smoothly, edits its fluid step to store FLOW_CLIP_FRAMES frames (48 by default) over the 16 s run (model.step.edit), then solves the lattice Boltzmann step on the CPU (solve.fluid).
Fixes the velocity legend clamp (0 to 45 mm/s) so the colours mean the same thing from frame to frame, sets a light theme and an iso view, and renders the model-only viewport at each field frame (results.frame then ui.render): velocity on the mid-slice, the bracket coloured by the flow beside it, and streamlines seeded upstream, coloured by speed.
Captions each frame with the elapsed flow time in a band below, drawn by the demo-video tool's standard-library TrueType caption drawer (tools/demo-video/caption.py, Inter SemiBold).
Encodes the frames at 12 fps (the settled wake held at the end) into the MP4 (H.264) and writes the settled still. --gif also writes a GIF (800 px, its own palette); it is not committed because it is several times larger than the MP4.

The clip shows the wake forming behind the upright and the drag settling; it does not shed, which needs a finer grid or a collision operator stable near τ⁺ = 0.5 (see issue #557). The geometry is the original upright-bracket SolidCraft recipe (the flow-past sample); nothing comes from a commercial product.