glow

The lit half of the combat effect family. Every effect in combat/ draws its light through combat_glow — one additive material carrying four forms — and this module is where the family agrees on what each instance-data lane means, leases the card a form is drawn on, and writes a frame's state onto it.

local Glow = require("@builtin::systems.effects.combat.glow")

local card = Glow.ball(ctx, "muzzle_bloom", position, 0.7)
Glow.write(card, {
    form = Glow.BLOOM, age = 0.3, color = { 1.0, 0.86, 0.55 }, gain = 8,
    a = 0.55, b = 1.4,
})

A rod covers the whole flight path and the shader lights the part of it the round has reached, so a tracer's geometry is seated once and nothing about it moves per frame.