Key points
- Claude Opus 5.5 Medium converted a Three.js project to Vanilla JS and WebGL in one thread.
- The resulting file was larger at 98KB compared to the original 77KB Three.js version.
- Willison noted the outputs were not identical and could not explain the differences.
Simon Willison published a report on 9 November 2026 detailing a test where Claude Opus 5.5 Medium generated 3D code without external libraries.reported The developer asked the model to port an existing Three.js project into Vanilla JavaScript and WebGL within the same conversation thread.The test shows an AI model can rewrite complex 3D code without needing special software libraries.The demonstration confirms Claude Opus 5.5 Medium can generate functional WebGL implementations from Three.js abstractions.
The evidence
Willison created a Nudibranch-themed Faberge Egg using Three.js, resulting in a 77KB file hosted on his static server.reported He then instructed Claude Opus 5.5 Medium, running in regular Claude Chat, to rewrite that project using only Vanilla JS and WebGL.reported The model produced a new version that was 98KB in size.
The decision
The test demonstrates that Claude Opus 5.5 Medium is capable of handling complex 3D modeling tasks without relying on Three.js.reported Willison observed that the model successfully generated the necessary WebGL code directly, removing the need for the abstraction layer provided by the library.
What to make of it
The two versions of the egg were not identical, and Willison stated he did not fully understand why the outputs differed. He linked to a transcript of the conversation where Claude explained the discrepancies, though the developer noted the differences did not significantly impact his workflow.
In practice
Simon Willison used Claude Opus 5.5 Medium to port a Three.js project to Vanilla JS in a single chat thread.reported The model generated a 98KB file from a 77KB original. Willison noted the outputs were not identical and could not fully explain the differences. He found the original Three.js code slightly easier to understand but rarely reviews such code.
Why it matters
- Developers can see that Claude Opus 5.5 Medium can generate Vanilla JS and WebGL code without Three.js.
- The port was completed in a single conversation thread, showing continuity in the model's context.
- The resulting file was larger than the original, increasing from 77KB to 98KB in this instance.
- The outputs were not identical, indicating potential variations in how the model interprets ports.
Topics: claude, three-js, javascript, generative-ai, llms
Updated
Then / now / next
Developers relied on libraries like Three.js to simplify WebGL coding for 3D web objects.
Claude Opus 5.5 Medium can generate equivalent Vanilla JS code directly from existing projects.
It remains unclear if this capability scales to more complex 3D scenes with higher fidelity requirements.
Story timeline
- Then Developers relied on libraries like Three.js to simplify WebGL coding for 3D web objects.
- 09 Nov 2026 The Web Is More Than Enough, by Paul Ford
- Now Claude Opus 5.5 Medium can generate equivalent Vanilla JS code directly from existing projects.
- Next It remains unclear if this capability scales to more complex 3D scenes with higher fidelity requirements.
The strongest doubt
Counterpoint from the sources
Willison found the original Three.js code slightly easier to understand, though he rarely reviews such code for these projects.
Try it
Port this Three.js code to Vanilla JS and WebGL.
Good result: Claude Opus 5.5 Medium generated a working 98KB Vanilla JS version of a 3D egg model.
Ask the article
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Your choice stays on this device. No public tally.Terms in this story
Three.js
A JavaScript library used to create and display animated 3D graphics on a web browser.
Vanilla JS
Pure JavaScript code written without the use of additional frameworks or libraries.
WebGL
A JavaScript API for rendering interactive 2D and 3D graphics within any compatible web browser.
Claude Opus 5.5 Medium
A specific model version of Anthropic's Claude AI, used in this test for code generation.
Questions readers ask
Can Claude Opus 5.5 Medium replace Three.js for 3D web development?
The model can generate Vanilla JS and WebGL code that functions without Three.js, as shown in Willison's test.
How does the file size compare between the two versions?
The Vanilla JS version was 98KB, while the original Three.js version was 77KB.
Did the ported code look exactly like the original?
No, Willison noted the outputs were not identical and could not fully explain the differences.
Connected stories
Reading receipt
- Claude Opus 5.5 Medium converted a Three.js project to Vanilla JS and WebGL in one thread.
- The resulting file was larger at 98KB compared to the original 77KB Three.js version.
- Willison noted the outputs were not identical and could not explain the differences.