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Three.js · 07 Shared Geometry and Cloning
Series contents · Technology map
Stage: Scene Coordinates, Cameras, and Geometry · Editable example · Storage ID: threejs-step-07
Goals and learning outcomes
- Reproduce the difference between shared and independent materials.
- Record the material owner.
Prerequisites
Prerequisite concepts: The Role of Normals, Smoothing. Prepare the result files and observation notes from unit 6.
Key concepts and explanations
Shared References
Multiple Mesh objects can reference one geometry or material. Changing a shared resource affects every object that references it.
Ownership
Cloning an object does not mean independently copying every GPU resource. Check the scope of sharing before modifying or releasing resources.
Practice setup
First read the execution-scope guidance on the example screen. The following environment is for extending the assignment in a separate project. Implement it yourself in an HTML and ES module project served by a separate local HTTP development server. Pin three and addons to the same installed version and record it.
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
- Prepare day-07.js and index.html in the external exercise project. Place three cubes that use the same geometry and material.
- Change the material color of one cube, then compare a version separated with material.clone.
- Save the output under the Shared reference input condition, then run again under the Individual cloned materials condition. Expected: Changing one cube’s color does not propagate to the other cubes. Compare with the actual screen and logs, and record the actual result and reasons for any differences in day-07-notes.md.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Material | Shared reference | Individual cloned materials | Changing one cube’s color does not propagate to the other cubes. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Reproduce the difference between shared and independent materials.
- Record the material owner.
Self-check
- Does clone also deeply copy geometry?
- When can shared resources be disposed of?
Official references
Linked example and execution scope
Example source · Runtime environments and limits
This is an editable browser experiment. Measurements vary with the current device and browser.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.
Next learning
Previous: Normals and Surface Orientation · Next: Light Types and Placement