display_curve

The chain's display transform in Luau, for a suite that reads a rendered pixel and has to say what light produced it.

__display__ runs on every frame the engine delivers, so a surface answering a known light value does not arrive at the frame as that value: it arrives as the Khronos PBR Neutral tone curve of it, encoded for a display. shownRGB is that pair composed — hand it the light a case authored and it answers the code values the capture should read.

local DisplayCurve = require("@builtin::tests.fixtures.display_curve")
local expected = DisplayCurve.shownRGB({ 0.8, 0.2, 0.2 })
-- … compare `expected` against the pixel the capture returned …

The curve mixes channels by their shared peak, so neutralCurve and shownRGB take the whole triple; a case holding a single channel still passes the three. srgbEncode is the transfer function alone, for a case that holds __display__ at curve = 0 and measures the encode by itself. srgbDecode is its inverse, for a case that reads such a frame back and needs the light a code value came from — dividing out the exposure the frame was captured under recovers the scene-referred value.

The formula is zero_display_neutral in src/engine/renderer/subsystems/post_process_renderer.rs, read on a light triple rather than on a fragment.