# coldstart The demo's opening title sequence, "COLD START". The whole picture is a pure function of one number — the time in seconds since the sequence began. `frameAt(t)` returns the widget tree for that instant and no state lives anywhere else, so the same `t` always produces the same image. That is the point of the design: the sequence can be advanced by the frame clock or jumped to any instant, and both give the same frame. It can therefore be looked at while it is being built, one moment at a time, instead of only in the one-and-a-half seconds it happens to be on screen. ## Driving it ```lua local Intro = require("preseed.coldstart") Intro.start() -- begin at t = 0 and show the screen Intro.update(dt) -- advance by dt * SPEED and repaint; call every frame Intro.stop() -- take it off the glass Intro.seek(6.6) -- jump to an instant without touching the clock Intro.time() -- where the sequence is now Intro.finished() -- has it reached DURATION ``` `DURATION` is 12 sequence seconds. `SPEED` is how fast those run against wall time, so the piece's real length is `DURATION / SPEED`. Every cue in the file is written in sequence seconds, which means changing `SPEED` restretches the whole sequence without moving any beat relative to another. ## Looking at it Because `seek` is deterministic, a whole contact sheet comes out of one call — in edit mode, with the engine paused: ```lua local Intro = require("preseed.coldstart") for i, t in ipairs({ 0.3, 0.75, 1.9, 2.5, 4.2, 6.5, 7.6, 9.0, 11.3 }) do Intro.seek(t) task.wait() tools.use("capture", "viewport", string.format("/source/tmp/intro/%02d.png", i)) end ``` ## The beats | sequence time | beat | |---|---| | 0.0 – 1.6 | a slit of light opens the black; three counts fire over magenta | | 1.6 – 3.6 | ORIGOZERO assembles letter by letter, then is thrown off frame | | 3.6 – 5.8 | COLD tears across a cyan field, mirrored beneath itself | | 5.8 – 8.6 | the title card: COLD / START on a magenta starburst | | 8.6 – 10.6 | the roll, ticking in from the left | | 10.6 – 12.0 | strobe to white, then the mark alone | A white strike covers each cut between beats, so a change of beat reads as an impact rather than a swap. ## Where it renders The sequence is a full-frame screen. A letterbox crops its type and a heavy grade dulls it, so the part that runs it clears both — see `preseed/parts/p_coldstart.module`.

# crt_scanlines A CRT line texture over the finished frame — the demo opener's grain. Every `period` framebuffer rows, `thickness` of them are darkened by `strength`. Because it reads `frag_coord`, the line pitch follows the real output resolution rather than any layout unit, so it looks the same whatever the frame is rendered at. | property | default | what it does | |---|---|---| | `period` | 6 | rows between one line and the next | | `thickness` | 2 | rows darkened out of each period | | `strength` | 0.30 | how far those rows are darkened, 0–1 | ## Why it is a shader The opener is a `zui` screen whose whole tree is rebuilt every frame. Drawn in that tree, this texture was one absolutely-positioned box per line — 240 nodes built, laid out and drawn every frame, which measured about half the sequence's frame cost. As a full-screen pass it costs one draw and touches no nodes. ## Using it `preseed/parts/p_coldstart` installs it on `enter` and removes it on `exit`: ```lua local shader = asset.resolve("crt_scanlines", "shader") tools.use("pp", "add", "crt_scanlines", { shader = shader, priority = 100 }) ```

# demo_fade The last pass in the demo's post chain (priority 200). It draws the letterbox bars and the fade to a solid colour, so every part is cut, held and faded through one pass rather than per-part geometry. `bars` is the height of each bar as a fraction of the frame, clamped to 0.45, and the bars are black. `fade` mixes the frame toward `col_r`/`col_g`/`col_b`, so `fade = 1` is a full dip to that colour. `preseed.fx` drives all five through `postprocess.setProperty` from `Fx.setFade` and `Fx.setBars`.

# glow <!-- zero:scaffolded-readme --> <!-- Replace the line below with what this shader provides and who consumes it, then delete both comment lines. --> TODO: describe this shader.

# fx A module script.