Open code, practice, and notes →
Download source with English comments · for reading
OffscreenCanvas · 16 Batching Particle Data
Series contents · Technology map
Stage: Rendering Lifecycle and Recovery · Editable example · Storage ID: offscreen-canvas-step-16
Goals and learning outcomes
- Learning outcome: explain the role of TypedArray. Input cases: 100 particles.
- Deliverable: byteLength and the range of particle coordinates. Explain the rationale for handling Ownership, linking it to the code.
Prerequisites
Prepare the experiment results for Patches and Versions from Unit 15, “Updating Scene State”.
Key concepts and explanations
TypedArray
Particle attributes can be stored in contiguous arrays. Define the stride and offset for each attribute clearly.
Ownership
Do not reuse a transferred array on the main thread. Receive summaries needed by the UI in separate messages.
Practice setup
First check the execution scope guidance on the example screen. The following describes the environment needed to extend the assignment in a separate project. The existing offscreen-canvas-01·02·03 are starting examples for supported browsers. Implement the new units in main-thread and Worker files in a separate local HTTP project. Check API and context support, and provide a main-thread fallback on a new Canvas if transfer fails. Preserve CSP and isolation, and record performance measurements yourself.
The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.
Practice tasks
- In src/day-16.js in a separate practice project, transfer Float32Array positions and draw the particles in the Worker. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: 100 particles. Baseline: Copy. Run under the baseline conditions, then record observations and errors in notes/day-16.md.
- Variable: Transmission; changed value: transfer. Run again through the same input path. Deliverable to save: byteLength and the range of particle coordinates. Hypothesis to check: The main-thread buffer is detached after transfer. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Transmission | Copy | transfer | The main-thread buffer is detached after transfer. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Required deliverable: byteLength and the range of particle coordinates. Results are available for both the baseline and changed conditions, allowing comparison of 2 conditions; input values and the execution environment are recorded together.
- The explanation of differences between the two conditions connects both concepts: TypedArray and Ownership. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does TypedArray affect in this exercise? Input cases: 100 particles.
- Variable: Transmission. Hypothesis to check: The main-thread buffer is detached after transfer. Did the actual results agree with the hypothesis? Explain the evidence in terms of Ownership.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
An interactive Batching Particle Data experiment with cleanup of the resources it uses.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.