Rumo effects

Example repository for the Effects section of the Rumo shop. It carries the rumo-effects topic, so Rumo finds it through the GitHub search API.

What is here

Path	What it is
rumo-manifest.json	what this repository offers: name, version, which Rumo it is for, where the files are
rumo-verification.json	the result of Rumo's own check that the content works
effects/crt-scanlines.rumoeffect	effect 1
effects/rgb-split.rumoeffect	effect 2
previews/*.webp	the small pictures shown in the shop list

CRT Scanlines

Dark bands between phosphor rows, a horizontal wobble that grows towards the edges and drifts with time, and a vignette.

Parameter	Range	Default
Lines	20 – 600	220
Depth	0 – 1	0.5
Wobble	0 – 0.03	0.006
Vignette	0 – 1	0.45

This is the one to try first if you want to know whether a custom effect runs at all: all three of its parts are visible on a flat colour, so a shape layer shows them. RGB Split does not — chromatic aberration needs texture detail, and a shape layer is one flat colour.

RGB Split

Chromatic aberration. Red is sampled a little further from the frame centre and blue a little closer, while green stays put; the displacement grows with distance from the centre, so the middle stays sharp and the edges fringe. A second parameter darkens the corners.

Parameter	Range	Default
Split	0 – 0.06	0.02
Vignette	0 – 1	0.35

One pass, no downscale, so it costs one full-resolution draw.

An effect is a WGSL module

.rumoeffect is JSON with the effect under effect:

{
  "kind": "rumo-effect",
  "formatVersion": 1,
  "name": "RGB Split",
  "effect": {
    "id": "rgb_split",
    "label": "RGB Split",
    "space": "display",
    "passes": [{ "entry": "fs_main", "shrink": 0 }],
    "params": [{ "key": "amount", "label": "Split", "kind": "float",
                 "min": 0.0, "max": 0.06, "default": [0.012] }],
    "source": "...WGSL..."
  }
}

The module declares exactly five bindings and no vertex stage:

@group(0) @binding(0) var input_tex: texture_2d<f32>;
@group(0) @binding(1) var input_smp: sampler;
@group(0) @binding(2) var<uniform> frame: Frame;      // size, time, pass_index, texels
@group(0) @binding(3) var origin_tex: texture_2d<f32>; // the untouched layer
@group(1) @binding(0) var<uniform> params: Params;

struct Params must list the declared parameters in the same order, as f32, vec2<f32>, vec3<f32>, vec4<f32>, mat3x3<f32> or mat4x4<f32>. The host supplies the vertex stage, so uv has a top-left origin and can be fed straight into textureSampleLevel. Colour maths is in display space (gamma-encoded 0–1) and layer textures are straight alpha.

Publishing your own

1. Put a rumo-manifest.json and a rumo-verification.json in the repository root, plus the content file and a webp or avif preview for each item.
2. Add the rumo-effects topic to the repository.
3. Keep it to four effects per repository and two shop repositories per account.

Rumo shows a repository only when the verification file is present, every item in it passed, the declared files exist, and the previews are webp or avif. Rumo also re-runs the WGSL validator on install and refuses a module it cannot compile, so a broken effect cannot reach the driver.

The verification file is produced by Rumo's own checker. The one in this repository was produced on the host with the engine's own naga front end (validate_source); Rumo re-checks on install.

Licence

MIT — see LICENSE. Use this module for anything, including commercially.