tinygltf v3 C

July 31, 2026 · View on GitHub

A minimal single-page demo that parses glTF/GLB in the browser using the tinygltf v3 C runtime compiled to WebAssembly, then renders the result with three.js.

web/
  loader.c        — C bridge: parse bytes, flatten primitives/materials/textures/nodes for JS
  index.html      — demo page (file picker + drag & drop)
  main.js         — three.js viewer consuming the WASM exports
  style.css
  Makefile        — Emscripten build
  gen_sample.py   — generates Cube.glb (small self-contained textured cube)
  Cube.glb        — sample model, generated with `make sample`

Requirements

An Emscripten SDK. The Makefile defaults to ~/work/emsdk (override with make EMSDK=/path/to/emsdk).

Build

$ cd web
$ make            # produces tinygltf_v3.js + tinygltf_v3.wasm
$ make sample     # generate Cube.glb (self-contained textured cube)
$ make serve      # python3 -m http.server 8000

Then open http://localhost:8000 and drop a .glb / .gltf file onto the page, or click Load sample.

Notes

Assets must be self-contained: GLB binary chunk or embedded data-URI buffers/images. External .bin / image file references are not resolved (no filesystem is linked into the module: -sFILESYSTEM=0).
Primitives must use float VEC3 positions (the common case); sparse accessors and double attributes are skipped with a warning message.
Image decoding happens client-side: raw image bytes are passed to createImageBitmap() and wrapped in a THREE.CanvasTexture.

C exports (loader.c)

All functions are exported as _tg3w_* on the Emscripten module:

Function	Description
`tg3w_parse(ptr, size)`	Parse GLB/glTF bytes (auto-detect), flatten model
`tg3w_clear()`	Free the current model and flattened buffers
`tg3w_last_error()` / `tg3w_error_message(i)` / `tg3w_error_count()`	Parse diagnostics
`tg3w_prim(i)`	Primitive record (material, mode, counts, buffer offsets; `nrm_offset`/`uv_offset` are -1 when absent)
`tg3w_positions()/normals()/uvs()/indices()`	Flattened vertex/index arrays
`tg3w_mesh_prim_start/count(m)`	Primitive range of a mesh
`tg3w_material_*`	PBR factors, alpha mode, base color texture
`tg3w_texture_source(i)`, `tg3w_image_bytes/size/mime(i)`	Texture image bytes
`tg3w_node_`, `tg3w_scene_`, `tg3w_default_scene()`	Scene graph