WebGLBackend

A renderer for a Scene, implemented per target (WebGL / Canvas / SVG).

Implements

Backend

Properties

stylesNeedDrawables

readonly stylesNeedDrawables: false = false

WebGL renders from the GPU flag/color textures, not the vector view — the drawables arg to updateLayerStyles is only stashed for toSVG export. So the engine may omit it on hot paths (per-frame declutter) to skip an O(n) rebuild.

Implementation of

Backend.stylesNeedDrawables

supportsPassThrough

readonly supportsPassThrough: true = true

Defined in: webgl/webgl-backend.ts:21

True if this backend supports pass-through (canvas/webgl yes, svg no).

Implementation of

Backend.supportsPassThrough

textLayerMode

readonly textLayerMode: "export-only" = "export-only"

Defined in: webgl/webgl-backend.ts:330

Labels are an export-only stash here (#219): the engine keeps the HTML overlay live on WebGL and pushes the placed set only when exporting — never per transform (zero per-frame cost).

Implementation of

Backend.textLayerMode

Accessors

gpuDevice

Get Signature

get gpuDevice(): Device

Defined in: webgl/webgl-backend.ts:61

The luma.gl Device powering this backend — exposed for GPU-side consumers (e.g. GPU layout).

Returns

Device

Methods

appendToLayer()

appendToLayer(delta): void

Defined in: webgl/webgl-backend.ts:181

O(new) incremental append: grow the existing GroupRenderer’s geometry buffers (capacity-doubling) and color/flag textures with only the appended tail, instead of rebuilding from full buffers. The engine calls this (not updateLayer) for appends.

The layer is always registered (via setLayers) before any append, so the renderer exists; if it somehow doesn’t, we no-op (nothing to grow from a delta alone). If a new geometry-type pass appears that can’t be grown incrementally (renderer.append returns false), fall back to a full rebuild via updateLayer so the result stays correct.

Parameters

delta

RenderDelta

Returns

void

Implementation of

Backend.appendToLayer

destroy()

destroy(): void

Defined in: webgl/webgl-backend.ts:572

Returns

void

Implementation of

Backend.destroy

drawPassThrough()

drawPassThrough(name, batch, mode): void

Defined in: webgl/webgl-backend.ts:223

Draw a batch into the layer’s accumulation buffer. mode: "replace-first" clears the layer’s buffer first (start of a full repaint), "replace-rest" continues a chunked full repaint without clearing, "append" draws on top (incremental).

Parameters

name

string

batch

DrawBatch

mode

"replace-first" | "replace-rest" | "append"

Returns

void

Implementation of

Backend.drawPassThrough

pickInstanced()

pickInstanced(x, y, exact): number | undefined

Defined in: webgl/webgl-backend.ts:507

GPU-readback pick (#141): resolve a screen point (CSS px) to the topmost pickable instanced link instance. Returns the decoded gl_InstanceID, -1 for background, or undefined when there are no pickable layers (the engine then falls through to other pick paths). exact: true (click) reads synchronously; exact: false (hover) uses the double-buffered PBO and may return the previous pointer position’s result with no stall. See PickReadback.

Parameters

x

number

y

number

exact

boolean

Returns

number | undefined

Implementation of

Backend.pickInstanced

readPixel()

readPixel(x, y): number[]

Defined in: webgl/webgl-backend.ts:561

Read a pixel from the offscreen framebuffer (renders first). Flips y for WebGL origin.

Parameters

x

number

y

number

Returns

number[]

readScreenPixel()

readScreenPixel(x, y): number[]

Defined in: webgl/webgl-backend.ts:550

Read a pixel from the ONSCREEN canvas default framebuffer after render(). Test aid. Coords are in CSS px; the onscreen buffer is device px, so scale by the buffer ratio.

Parameters

x

number

y

number

Returns

number[]

removeInstancedLayer()

removeInstancedLayer(name): void

Defined in: webgl/webgl-backend.ts:315

Remove an instanced primitive layer by name.

Parameters

name

string

Returns

void

Implementation of

Backend.removeInstancedLayer

removePassThroughLayer()

removePassThroughLayer(name): void

Defined in: webgl/webgl-backend.ts:215

Remove a pass-through layer.

Parameters

name

string

Returns

void

Implementation of

Backend.removePassThroughLayer

render()

render(): void

Defined in: webgl/webgl-backend.ts:401

Returns

void

Implementation of

Backend.render

resize()

resize(width, height): void

Defined in: webgl/webgl-backend.ts:350

Resize the onscreen canvas drawing buffer (luma owns it via useDevicePixels), recompute the clip matrix at the new size, push the new viewport to every renderer (screen-mode point sizing) and recreate the offscreen export framebuffer. The engine re-pushes layers + renders after. Globe mode reads this.width/height per draw, so it follows automatically.

Parameters

width

number

height

number

Returns

void

Implementation of

Backend.resize

setGlobeMode()

setGlobeMode(on, texW?, texH?): void

Defined in: webgl/webgl-backend.ts:385

Enter/leave globe mode. texW/texH = equirect bake size. Idempotent re-entry resizes.

Parameters

on

boolean

texW?

number = 2048

texH?

number = 1024

Returns

void

setGlobeRotation()

setGlobeRotation(m): void

Defined in: webgl/webgl-backend.ts:399

Update the globe rotation (mat3, column-major) and repaint. No re-bake.

Parameters

m

Float32Array

Returns

void

setInstancedLayer()

setInstancedLayer(layer): void

Defined in: webgl/webgl-backend.ts:242

Register/replace a GPU-instanced primitive layer (the network rendering lane). Optional — only the WebGL backend implements it; other backends omit it, so network instanced rendering is WebGL-only (small-N / export go through the PathContext emitter).

Parameters

layer

InstancedLayer

Returns

void

Implementation of

Backend.setInstancedLayer

setLayers()

setLayers(newLayers): void

Defined in: webgl/webgl-backend.ts:85

Parameters

newLayers

RenderLayer[]

Returns

void

Implementation of

Backend.setLayers

setPassThroughLayer()

setPassThroughLayer(layer): void

Defined in: webgl/webgl-backend.ts:209

Parameters

layer

PassThroughLayer

Returns

void

Implementation of

Backend.setPassThroughLayer

setTextLayer()

setTextLayer(texts): void

Defined in: webgl/webgl-backend.ts:334

Retain the screen-space labels for toPNG()/toSVG() (#219). No render — the set is not drawn to screen (the HTML overlay is); an O(1) reference swap, safe to call at any frequency.

Parameters

texts

readonly TextData[]

Returns

void

Implementation of

Backend.setTextLayer

setTransform()

setTransform(t): void

Defined in: webgl/webgl-backend.ts:338

Parameters

t

ViewTransform

Returns

void

Implementation of

Backend.setTransform

snapshotPassThrough()

snapshotPassThrough(): void

Defined in: webgl/webgl-backend.ts:240

No-op for WebGL: the accumulation FBO persists across gestures and PassThroughGL.fboTransform already records the reference transform (set on the last clear), so the composite blit can offset it during a pan with no extra snapshot. (The canvas backend, by contrast, must copy the canvas here because it has no retained FBO.)

Returns

void

Implementation of

Backend.snapshotPassThrough

styleInstancedLayer()

styleInstancedLayer(name, highlight): void

Defined in: webgl/webgl-backend.ts:324

Shader-driven highlight (#162): set the layer’s highlight uniforms (+ optionally rewrite its per-instance selected flags) with no geometry rebuild — a hover is a uniform change.

Parameters

name

string

highlight

InstancedHighlight

Returns

void

Implementation of

Backend.styleInstancedLayer

toPNG()

toPNG(): string

Defined in: webgl/webgl-backend.ts:479

Returns

string

Implementation of

Backend.toPNG

toSVG()

toSVG(): string

Defined in: webgl/webgl-backend.ts:487

Returns

string

Implementation of

Backend.toSVG

updateInstancedLayer()

updateInstancedLayer(layer): void

Defined in: webgl/webgl-backend.ts:276

Update-in-place for instanced layers: if the layer already exists as the matching primitive type, call update() (GPU sub-upload, no teardown). Lines/arrows/half-arrows return false from update() when a structural property changed (samples, half-flag) — fall back to setInstancedLayer (destroy+recreate) in that case. Also recreates when the primitive type changes (e.g. lines → arrows) OR when the layer’s pickable state no longer matches the existing renderer’s pick-model presence (toggling pickLinks builds/drops the id-encoded pick model, which update() can’t do in place — see #141/#179).

Parameters

layer

InstancedLayer

Returns

void

Implementation of

Backend.updateInstancedLayer

updateLayer()

updateLayer(name, layer): void

Defined in: webgl/webgl-backend.ts:115

Replace a layer’s geometry + tables. When the layer’s renderer already exists and needs no pass it was built without, it is updated IN PLACE (GroupRenderer.replace): geometry buffers and tables are rewritten through the retained Grow* objects (which grow + rebind on overflow) and the Models/pipelines are REUSED. The hover overlay re-targets a different drawable on every pointer move, so this path must not churn GPU objects per event (#218). It is still a full GEOMETRY replace, never a same-count recolor shortcut: equal drawable counts do NOT imply unchanged geometry, so the buffers are always rewritten. Styles-only changes go through updateLayerStyles; appends through appendToLayer (O(new)). Destroy + rebuild remains only for a structural change (a geometry-type pass appearing that the renderer lacks — e.g. an overlay created points-only later highlighting a path).

Parameters

name

string

layer

RenderLayer

Returns

void

Implementation of

Backend.updateLayer

updateLayerFlags()

updateLayerFlags(name, flags): void

Defined in: webgl/webgl-backend.ts:163

Flags-only update (#208): rewrite ONLY the flags texture — colour tables, geometry and the stashed vector view untouched, zero CPU-side copies. A zoom frame with declutter uploads drawableCount bytes instead of updateColors’ 9×. The vector view (toSVG reads it) is NOT patched here — that would be an O(drawables) per-frame loop for an export-only consumer; the live view is retained and folded in at toSVG().

Parameters

name

string

flags

Uint8Array

Returns

void

Implementation of

Backend.updateLayerFlags

updateLayerStyles()

updateLayerStyles(name, tables, drawables?): void

Defined in: webgl/webgl-backend.ts:141

Styles-only update: rewrite the palette/flags textures, refresh the stored vector view (toSVG reads it), leave geometry buffers untouched. drawables omitted ⇒ keep the previously-stored vector view (export may lag the textures until the next update with it).