film

The clock, the shot table and the palettes of GREEN SKY. Every other slice talks to this module and to nothing else.

The clock

A fixed 1/24 s per rendered frame, ignoring the real frame delta. The film is therefore byte-identical on every run whatever the frame rate, so it can be recorded a frame at a time and retimed on the host.

Film.FPS         24
Film.FIXED_DT    1/24
Film.DURATION    122 seconds

scenes/main.scene's entrypoint calls Film.build() once on load and Film.tick() once per frame. There is no cutscene, no coroutine timeline and no task.wait chain anywhere in the demo.

The shot table

Film.SHOTS — eighteen entries, { n, seconds, act, name, brief }. seconds is the only timing authority in the film; greensky/camera owns where each set-up stands. Shot numbers are stable and are never renumbered, because every slice keys off them.

Film.shotAt(t)      -> the shot on screen at t, and seconds into it
Film.shotStart(n)   -> when shot n begins

Registering a slice

local Film = require("greensky.film")
local M = {}
function M.build() end      -- once, on scene load
function M.update(c) end    -- every frame
Film.register("pan", M, 10) -- lower order ticks first

The context c every update receives:

Film.arcAt(t) gives those last three at any time, so a slice can ask what act III looks like without waiting for it.

Two palettes, and they are not the same thing

Film.PALETTE is the light — what the sun, the sky and the ambient are doing in the world, per act, plus the discharge. greensky/sky reads it every frame.

Film.PAL is the photograph taken of that light — the response of the camera's negative, per act. greensky/camera reads it every frame and writes it into the gs_grade post-process pass. Its fields are ev (exposure compensation in stops), exposure, contrast, pivot, saturation, vignette, vigInner, grain, and the ASC-CDL triplets lift (offset, moves the blacks), gain (slope, the whites) and gamma (power, the mids).

Both carry dry, storm, clear and flash, and both are interpolated by the same c.storm / c.clear ramps, so the light and the photograph of it always agree about which act it is.

Film.mixGrade(a, b, x) mixes two Film.PAL entries.

Every gain in Film.PAL is at or below 1 on purpose: the post chain is display-referred and hard-clipped at 1.0, so a gain above 1 clips the image rather than opening it up. Level lives in ev, in stops.

The site

Film.SITE — the numbers more than one slice needs about the place: pan radius, runway length and width, hangar position, cloud base and top, the cloud volume's horizontal extent, where the storm enters and leaves, and how deep the flood gets. Everything must live inside 8 km of every camera station, because the far plane is hard-fixed at 8000.

Curves

Film.ramp(t, a, b)    smoothstep, 0 before a and 1 after b
Film.lerp(a, b, x)
Film.mix3(a, b, x)    mix two {r, g, b}
Film.clamp01(x)

Files

film.module/init.luau   this module
../design/spec.md       read this before changing any of it
../design/shotlist.md   the eighteen shots as written