Glossary

Terms used across these docs.

Adapter / device — a handle to a physical GPU, and the logical connection used to create resources and submit work. See the WebGPU primer.

Bind group — a bundle of GPU resources (buffers, texture views, samplers) attached to a shader before a draw/dispatch, matching a declared layout.

Bloom — a glow post-process: extract bright pixels, blur them, add them back. See Bloom.

Cell — one glyph slot in the grid, cellSize device pixels square. A column is a vertical stack of cells.

Chromatic aberration — a CRT artifact where color channels are offset slightly, splitting R/B from G along an axis.

Compute pass — GPU work that runs a compute shader over a grid of workgroups and reads/writes storage buffers, with no render attachment. Here: the simulation step.

Column — one falling stream of rain; the per-column state record (headY, speed, depth, tailLength, seed). Stored in a storage buffer. See Data model.

Device pixels (drawing-buffer pixels) — the canvas’s actual pixel resolution, CSS px × devicePixelRatio. All shader math here is in device pixels.

DPR (devicePixelRatio) — ratio of device pixels to CSS pixels; the component multiplies fontSize by it so cellSize is in device px.

fwidth — a shader built-in giving the screen-space rate of change of a value (≈ how much it changes between adjacent pixels). Used to size the anti-aliasing band to ~1px. See Glyph rendering.

HDR target — an offscreen rgba16float texture that can hold values above 1.0, giving bloom and tone-mapping real range.

Particle system — a simulation of many independent points with position/velocity. The rain columns are a 1D particle system.

SDF (signed distance field) — an image where each texel stores the signed distance to the nearest glyph edge (negative outside, positive inside, zero at the edge). Lets text render crisp at any scale. See SDF atlas.

8SSEDT — 8-points Signed Sequential Euclidean Distance Transform, the algorithm used to compute the SDF from a rasterized glyph.

Separable blur — a 2D Gaussian blur done as two cheap 1D passes (horizontal then vertical) instead of one expensive 2D kernel. Used by bloom.

smoothstep — a shader built-in giving a smooth 0→1 ramp between two edges; used with the SDF value to get anti-aliased coverage.

Storage buffer — GPU memory that shaders can read and write, indexable as an array. The Column[] state lives here.

Swap chain — the canvas’s presentable surface; the final pass writes to it.

TGSL / 'use gpu' — TypeGPU’s mechanism for writing shader logic in TypeScript; functions tagged 'use gpu' are compiled to WGSL at build time by unplugin-typegpu.

Tone-mapping — mapping (possibly >1.0) HDR colors into the 0..1 display range. This project clamps rather than using Reinhard (see CRT).

Uniform buffer — small, read-only-in-shader GPU memory broadcast to every invocation; the per-frame parameter block (Uniforms).

WGSL — WebGPU Shading Language, the language GPU shaders compile to.