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React Three Fiber · 22 demand Rendering

Series contents · Technology map

Stage: demand Policy and Performance Verification · Editable example · Storage ID: react-three-fiber-step-22

Goals and learning outcomes

Prerequisites

Unit 22 continues using the deliverables and experiment records from Unit 21.

Key concepts and explanations

Render on Demand

frameloop='demand' requests frames when changes occur. It can avoid continuous rendering in a stationary scene.

Manual Invalidation

React may not know when you change an object directly through a ref. Request the next frame with invalidate to reflect the change on screen.

Practice setup

First check the execution scope guidance on the example screen. The following describes preparation for extending the assignment in a separate project. Use JSX in a separate React Vite project. Record compatible major versions of React and @react-three/fiber, the Three.js version, and the lockfile. This course uses stable WebGL-based APIs and does not mix in alpha WebGPU APIs. Handle frame updates with useFrame and ref.

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

  1. Set Canvas frameloop to demand in src/DemandScene.jsx.
  2. Change group.rotation.y and call invalidate in the button Effect.
  3. Record frame counts for 5 stationary seconds and 5 button interactions in always and demand.

Variables to observe

VariableBaselineChangeExpected change / hypothesis
frameloopalwaysdemandStationary frames decrease, while button changes should remain visible.

Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.

Completion criteria

Self-check

  1. Is invalidate an immediate synchronous render command?
  2. Do multiple invalidate calls guarantee the same number of frames?

Official references

Linked example and execution scope

Example source · Runtime environments and limits

This is an actual React Three Fiber Canvas experiment. A browser with WebGL support is required.

Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.

Next learning

Previous: Instance Selection and Bounds · Next: demand and Ending Motion

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