Interaction
3D earns its place by explaining something
A 3D scene can reveal a product, a space or a transformation. When it only demonstrates technique, it usually takes more from the page than it gives.
The useful test
Before building a scene, ask what the visitor understands after interacting with it that a photograph or a short sequence could not show as clearly. A product configurator, spatial explanation or controlled before-and-after may justify depth. Decorative particles do not.
The cost is wider than file size
WebGL uses download bandwidth, graphics memory, battery and main-thread time. It also introduces failure modes: a missing graphics context, a slow integrated GPU, a hidden tab that keeps rendering or a scene that loses its context.
A production fallback
The message and controls remain in HTML. A static visual is the first frame, the scene loads after the page, rendering pauses outside the viewport and reduced motion never depends on the animation. If performance drops, the site keeps the poster and disposes of the scene.
Decisions from real projects
Diamond Lux Kopaonik kept a WebGL diamond on capable devices because it carried the visual idea. Halo City Leskovac removed its crystal scene during redesign because visitors on modest phones and weak connections needed a faster route. Both were design decisions.