feat(gsplat): decouple streaming from rendering for autoRender=false

[mvaligursky]

GSplat LOD streaming (octree evaluation + file loading) previously ran only in the render path, so an app with app.autoRender = false stopped streaming entirely — an idle/on-demand app could not load splats in the background. This decouples the CPU streaming pass from rendering so it runs every frame regardless, and adds a frame:request event so apps can render on demand when there is new data to show.

Changes:

• Split the per-frame gsplat work into a CPU streaming pass (LOD evaluation, file loading, world-state creation; GPU resource creation only) and the render pass (work-buffer bake, sort, draw). The streaming pass runs every frame from the GSplatComponentSystem via app.on('framerender'), independent of whether a frame is rendered.
• The render path still runs streaming inline for managers created during that render (startup / topology changes), deduped against the tick with a per-frame token, so the streaming work runs at most once per frame and any rendered frame is self-consistent.
• Result: background streaming progresses with app.autoRender = false, while the GPU stays idle until there is something new to draw.

API Changes:

• New event GSplatComponentSystem#frame:request (EVENT_FRAMEREQUEST = 'frame:request'). Fired once per frame, after the component/script updates and before rendering, when streaming has produced new data to show or a CPU-sort result is ready to apply. A typical handler sets app.renderNextFrame = true:

  app.autoRender = false;
  app.systems.gsplat.on('frame:request', () => {
      app.renderNextFrame = true;
  });

  Note: adding/removing cameras, layers, or gsplat components (and other changes the app makes itself, e.g. camera movement) need to trigger a render; frame:request covers asynchronous streaming changes only. frame:ready is unchanged and remains the capture/accuracy signal.

Examples:

• New gaussian-splatting/simple-on-demand — a single (non-streamed) splat rendered on demand.
• gaussian-splatting/lod-streaming-sh and gaussian-splatting/downtown updated to demonstrate on-demand rendering: render every frame during load + reveal, then switch to autoRender = false and render on frame:request, camera movement, and resize.

Performance:

• No change to the rendered output or steady-state cost (autoRender = true behaves identically; the render-path streaming call is a deduped no-op). On-demand apps now stay GPU-idle when the scene is static while continuing to stream in the background.

[github-actions]

Public API report

This PR changes the public API surface (+1 / −0), per the docs' rules (@ignore / @Private / undocumented are excluded).

Show API diff

+GSplatComponentSystem.static EVENT_FRAMEREQUEST: string

Informational only — this never fails the build.

[Copilot]

Pull request overview

This PR makes GSplat LOD streaming progress even when app.autoRender = false by moving the CPU-side streaming work (LOD evaluation + resource loading/world-state creation + GPU resource creation) out of the render-only path and into a per-frame tick. It also introduces a new frame:request event to support on-demand rendering when streaming (or async CPU sorting) produces new visual data.

Changes:

• Added a per-frame GSplat CPU streaming tick driven from GSplatComponentSystem via app.on('framerender'), independent of whether a frame is rendered.
• Split GSplat manager per-frame work into updateStreaming(token) (streaming/world-state) and update() (render-path bake/sort/draw), with per-frame token deduplication.
• Updated / added examples to demonstrate switching to on-demand rendering and rendering in response to frame:request, camera movement, and resize.

Reviewed changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/scene/gsplat-unified/gsplat-manager.js	Adds updateStreaming(token) + dedup token and moves cooldown ticking into the streaming pass.
src/scene/gsplat-unified/gsplat-director.js	Introduces director-level streaming tick, stream token, and frame:request emission.
src/framework/components/gsplat/system.js	Adds EVENT_FRAMEREQUEST docs and hooks framerender to drive streaming even when rendering is skipped.
examples/src/examples/gaussian-splatting/simple-on-demand.example.mjs	New example showing on-demand rendering with a non-streamed splat and camera-driven renders.
examples/src/examples/gaussian-splatting/simple-on-demand.controls.jsx	Control panel for the new on-demand example.
examples/src/examples/gaussian-splatting/lod-streaming-sh.example.mjs	Updates to demonstrate rendering on frame:request, camera movement, and resize after reveal.
examples/src/examples/gaussian-splatting/downtown.example.mjs	Updates to demonstrate rendering on frame:request, camera movement, resize, and UI changes after reveal.

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