Card Rail

The cards do not crawl past on a loop. They are flicked: the rail leaves at speed, decelerates for well over a second and comes to rest about a card further along, the way a carousel behaves under a thumb rather than under a timer. A title holds the top of the frame and does not move with them.

The plane is tilted, and that is the whole look

The rail is not flat to the camera. Measured on the card edges of a recording, the horizontal scale grows 0.000825 per pixel of height about the frame's own centre line — the foot of a card is a fifth wider than its head — while horizontals stay horizontal and the type stays upright. That is a plane rotated about a horizontal axis under perspective, and it is why a row of plain rectangles reads as a surface receding into the frame rather than as a filmstrip.

DEPTH, TILT and HORIZON are the three numbers that describe it, and they are deliberately separate from the card metrics: change the card size and the plane does not move. HORIZON is the height at which the plane is exactly life-size — above it the rail is smaller and further away, below it nearer and larger. It is solved, not chosen: the card's width at two heights puts it most of the way down the visible card rather than at the frame's middle.

Flicks add up

flicks is how many times the rail is pushed and every the frames between one leaving and the next. They are a sum, not a queue: each flick is the same measured curve started every frames after the last, so a flick begun while the one before it is still creeping carries that creep with it — which is what repeated swipes actually do. The default is three, thirty frames apart, which carries the rail about three cards along.

That is also why the card lists are worth filling out. Three flicks show six cards; five entries would start repeating on screen.

The flick is measured

FLICK is the curve off the recording. It peaks at 29px a frame three frames in and is still moving at 2px a frame a second later. No standard ease has that tail — a cubic-out arrives four times too early and a spring overshoots something that never overshoots.

And the travel is not one card pitch. A rail that advanced by exactly one pitch would be an assumption; measured, the recording's travels 333 where its pitch is 325. A flick ends where the momentum ran out, not on a snap, and those eight pixels are the difference between a carousel and a surface somebody pushed.

Cards, and cards made elsewhere

images, titles, notes and tags are parallel lists — one entry per card — and the rail repeats them rather than running out — though with three flicks you want at least six real ones, or the repeat shows. The rail has a beginning, though: nothing is drawn before the first card, because a loop that wraps round puts a card in the empty half of the frame the scene opens on.

Leave the text fields blank and the picture becomes the whole card. That is not a special case for its own sake — it is what lets a card designed somewhere else be handed in as one image.

Notes

backdrop takes two colour stops or one picture. A picture because a brand backdrop is often not a gradient at all: the recording this was measured from has corners that satisfy a linear fit to within five parts in 235, and a middle forty levels darker than that fit predicts — a mesh or a painted plate, not something two stops can be talked into.

from may be negative, which opens the scene already in flight. That is how the recording starts, and it is often what you want at the head of a video.

Installation

$ pnpm dlx shadcn@latest add @snapcn/card-rail

Component code

The exact file shadcn add copies into your project.

Usage

// src/Root.tsx
import { Composition } from "remotion";
import { CardRail } from "@/components/snap-cn/card-rail";

const Rail = () => <CardRail heading="Browse scenes" />;

export const RemotionRoot = () => (
  <Composition
    id="CardRail"
    component={Rail}
    durationInFrames={54}
    fps={30}
    width={1280}
    height={720}
  />
);

Props