particle op• Data kinds: table → table
• Call: import gfx2d; gfx2d.particle_step(state, dt, gravity=(0.0, 98.0), drag=0.0) (or opsgfx2d.get("particle_step"))
Advance a particle state by `dt` seconds. Returns a new dict.
Semi-implicit (symplectic) Euler::
v <- v + (g - drag*v) * dt
p <- p + v * dt
age <- age + dt
which makes the closed form exact and checkable: with `gravity=(0,0)` and
`drag=0 the position after k steps is p0 + v0*k*dt`, and with drag
the speed is `v0 * (1 - drag*dt)**k`. Both are compared as equalities in
the test suite.
`gravity is (gx, gy) in px/s^2, positive gy` pulling down the
screen. The input dict is never mutated.
Raises ValueError: `dt <= 0; drag * dt >= 1`, which is the point where
explicit drag stops decaying the speed and starts reversing it — an
instability that otherwise shows up as particles flying backwards rather
than as an error.
• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).
• Operator provenance and references — the sources of the research/methods this op family came from.
• The canonical algorithm (author, year) and its uses are named in the family usage guide above.
• gfx2d_scene — py -3.11 examples/gfx2d_scene.py
table as input)particle)particle_emit · particle_render
*Provenance: gfx2d.py — GFX2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.