GltfModel

In-memory model of a parsed glTF 2.0 asset, produced by GltfReader. Carries enough of the spec to drive textured + lit mesh rendering for 3D Tiles content; not a full glTF compliance representation.

The shape is intentionally flat and copy-free where possible — every primitive owns plain FloatArray / ShortArray / IntArray buffers ready for GPU upload. Materials reference images by index into images; per-image bytes carry the MIME type so a platform-side decoder can hand the bytes off to PNG/JPEG decode without inspecting the buffer.

Out of scope: full PBR (metallic/roughness textures, normal maps, occlusion, emissive), skeletal animation, morph targets, KHR_draco_mesh_compression. Future PRs can add them without changing the shape of consumers — extra optional fields on the primitives / materials.