This is a monorepo centered on `@google/model-viewer`, a production web component that renders glTF/GLB 3D models in the browser using Three.js and Lit. The core package provides a `<model-viewer>` custom element with a rich feature surface: WebXR/Scene Viewer/Quick Look AR, animation controls, camera orbit/perspective controls, environment lighting, hotspots/annotations, a mutable scene-graph API, lazy loading, and post-processing via a companion `model-viewer-effects` package. In addition to the library itself, the repo contains `space-opera`, a Redux + Lit-based interactive editor for configuring model-viewer snippets and editing glTF materials, plus a full documentation/examples site and render-fidelity tooling that performs golden-image screenshot comparisons across renderers. Although the dominant character is an application/library monorepo, it also includes research-grade visual fidelity workflows and color science work around tone mapping.