ghee for Python

pip install ghee-render: one package, two surfaces. It embeds the ghee renderer, and it provides the Python sugar for writing a procedural scene.

Build the wheel yourself with maturin:

maturin build --release --compatibility linux

Use

To use the ghee renderer:

import ghee

h = ghee.open(
    "scene.json",      # a path, the JSON text of a scene, or a dict
    output="st7789",   # a driver name, "kms", or None for headless
    opts={"width": 240, "height": 240, "backlight": 26},
    width=None, height=None,   # a headless size, a panel states its own
    fps=30,            # pace cap, None runs free
    stats=8090,        # console port, ("0.0.0.0", 8090) binds elsewhere
    stream_max=None,   # h264 stream cap: pixels, or a fraction of the render size
    verbose=False,
    timestep=None,     # pin time to frame*S for a reproducible render
)

h.set_param("gain", 1.5)                 # a scene param
h.set_param("snap", 1.0, pass_="hold")   # the param of one pass
h.set_param("hold.snap", 1.0)            # the same param, dotted

h.feed("level", bars)      # bytes, bytearray, memoryview, array, numpy, numbers
tick = h.frame()           # {"frame": 12, "time": 0.4, "dt": 0.0166}
tick = h.skip()            # the same tick, with no draw

h.size          # (width, height)
h.components    # 3 for RGB, 4 for RGBA
h.pixels()      # the last frame, row-major (height, width, components)
h.close()       # also a context manager

What each call does

set_param sets a live uniform, no recompile. A bare name is the scene param, else the param of the first pass that declares it.

feed holds the data for one declared array, and the next frame consumes it once. A uint8 buffer reaches the texture as byte / 255, a float32 buffer passes through. An array keeps its texture data until a feed changes it.

frame draws and hands the frame to the output. time is the wall clock since the first frame, dt is the measured frame period, and timestep pins both to frame * S.

skip takes the tick and draws nothing, the panel keeps its last frame.

stats serves the console on 127.0.0.1, and a (host, port) pair binds it elsewhere. Anyone who reaches the port can change params, so bind beyond loopback only on a network you trust. docs/http.md holds the API. This console shows the host's own scene, param changes apply, and scene switching and recompiles are refused. The video stream advances with frame(): viewers see a new frame only when the host draws one.

Rules

ghee is thread-affine: open a handle on one thread and use it on that same thread, a call from another thread raises RuntimeError.

A scene, GLSL or param error raises ValueError, a driver or system error raises RuntimeError.

frame() releases the GIL, so the host's other threads run while it renders.

Python scenes

The shim is used to write a procedural scene. A PEP 723 scene should declare ghee-render inline:

#!/usr/bin/env -S uv run --script
# /// script
# dependencies = ["ghee-render"]
# ///

The shim gives:

• ghee.Scene / Pass / Param / ArrayInput / Channel: build the scene
• ghee.Arg, ghee.args([...]): argument declarations, and the -- --help answer
• @ghee.feed("name"): the values of a named array, each tick. A uint8 buffer, bytes or a numpy uint8 array
• @ghee.tick: a hook for each tick, with ghee.set_param(name, value) and ghee.skip()
• ghee.run(scene): the handshake, then the tick loop

Direct mode

The same scene file runs two ways. When ghee starts it, as ghee render spectrum.py or from a scenes directory, run() feeds ghee over the wire protocol. When you run the file itself, run() opens the embedded renderer and renders directly:

./spectrum.py --output kms --frames 300
./spectrum.py --bins 32 --output none --size 320x240 --frames 1

ghee sets GHEE_WIRE=1 in every scene process it starts, and run() tells the two apart by it.

The scene takes its own arguments first, then these:

• --output NAME: a driver name, kms, or none for a headless render (default kms)
• --size WxH: the render size. A display or a panel states its own
• --fps N, --stats PORT, --timestep S: as ghee render takes them
• --frames N: 0 runs until SIGINT or SIGTERM (default 0)

The feeds, the hooks and ghee.skip() work the same. The tick keeps its wire shape, with params empty. If one of your own arguments collides with these names, argparse says so.

What the wire carries

The wire suits small per-frame data. Megabyte-scale data costs a serialization and two copies for each frame, and on a small Pi that shows up as a low frame rate. A data-heavy host takes ghee.open instead: the renderer in the same process, no pipe.