forked from 1b-agent/fieldcraft-upstream
Christian Svensson
8201f9a954
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.
40 lines
2.5 KiB
Markdown
40 lines
2.5 KiB
Markdown
# Flow-past clip
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`make.py` regenerates the gallery clip and still of the `flow-past` sample (docs/examples.md):
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`docs/media/examples/flow-past-transient.mp4` (the start-up transient of air flowing past the
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L-bracket, from the uniform 25 mm/s initial field to the settled wake) and
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`docs/media/examples/flow-past-flow.png` (a clean iso render of the settled flow).
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```sh
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python3 tools/flow-clip/make.py # build, run, encode into docs/media/examples
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python3 tools/flow-clip/make.py --no-build # with the release binaries already built
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python3 tools/flow-clip/make.py --frames /tmp/f # also keep the rendered pictures
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python3 tools/flow-clip/make.py --gif # also write a GIF (not committed; larger)
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```
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Needs Python 3 (standard library only), a display for the FieldCraft window (the pictures are
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drawn offscreen with `ui.render`, so a locked or virtual display is fine — on a headless machine
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run it under `xvfb-run`), and `ffmpeg` with libx264 on the `PATH` (or `FFMPEG`). It honours
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`CARGO_TARGET_DIR`; set `FIELDCRAFT_GPU=software` for a software renderer.
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What it does:
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1. Builds `fieldcraft` and `fieldcraft-cli` (release) and starts the app with `--control PORT`.
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2. Opens the `flow-past` sample and, so the transient plays smoothly, edits its fluid step to
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store `FLOW_CLIP_FRAMES` frames (48 by default) over the 16 s run (`model.step.edit`), then
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solves the lattice Boltzmann step on the CPU (`solve.fluid`).
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3. Fixes the velocity legend clamp (0 to 45 mm/s) so the colours mean the same thing from frame
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to frame, sets a light theme and an iso view, and renders the model-only viewport at each
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field frame (`results.frame` then `ui.render`): velocity on the mid-slice, the bracket
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coloured by the flow beside it, and streamlines seeded upstream, coloured by speed.
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4. Captions each frame with the elapsed flow time in a band below, drawn by the demo-video tool's
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standard-library TrueType caption drawer (`tools/demo-video/caption.py`, Inter SemiBold).
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5. Encodes the frames at 12 fps (the settled wake held at the end) into the MP4 (H.264) and writes
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the settled still. `--gif` also writes a GIF (800 px, its own palette); it is not committed
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because it is several times larger than the MP4.
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The clip shows the wake forming behind the upright and the drag settling; it does not shed, which
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needs a finer grid or a collision operator stable near τ⁺ = 0.5 (see issue #557). The geometry is
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the original upright-bracket SolidCraft recipe (the `flow-past` sample); nothing comes from a
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commercial product.
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