MeshGrab — WebGL geometry inspector

Capture WebGL vertex buffers and textures at upload time, classify the attributes, and export a glTF 2.0 binary.

MeshGrab shows you what a web page actually uploaded to the GPU. When a WebGL page renders a 3D model, the geometry that reaches the driver is not always the geometry the source asset describes. Attributes get packed, quantised, padded, or dropped somewhere in the pipeline. MeshGrab hooks the WebGL buffer and texture upload calls before any page script runs, captures what goes through them, and reports it as it really is. HOW TO USE Install, open the page you want to inspect, click the MeshGrab icon and choose "Enable on this site". That grants access to that one origin and reloads the page once, so the hooks are in place before the page's scripts run. Every later visit to that site is captured automatically. There is no on-page UI; nothing about the page changes. The popup shows the inferred vertex and triangle counts, every attribute it detected with its real GPU format, and any textures captured. Export GLB writes a glTF 2.0 binary you can open in any glTF-capable tool. If the popup reports that no uploads were seen, the geometry either reached the GPU before the hooks ran or has not uploaded yet. Trigger a fresh upload — reload, or switch models if the page has a picker. Geometry often uploads lazily, well after the model first appears on screen. WHAT IT DETECTS POSITION float vec3 NORMAL float vec3, or byte/short packed vec4, unpacked on export TANGENT float vec4, verified against the normal TEXCOORD_0 float vec2 indices 16- or 32-bit textures original encoded bytes, kept from the source blob Attributes are identified by content, not by assuming a layout. A float vec4 is only labelled a tangent if it is unit length, carries w = +/-1, and sits perpendicular to the normal. Normals are separated from positions by unit-length testing. Vertex count is inferred by byte-weighted agreement across buffers, so small helper meshes such as ground grids and gizmos cannot outvote the model. A per-vertex buffer holding a single value across the whole mesh is reported as a dead attribute — bandwidth being paid for and not used. LIMITS Worth knowing before you rely on an export: - Interleaved vertex buffers are not handled. If a page packs position, normal and UV into one buffer, MeshGrab will not find a mesh. - Quantised positions stored as normalised integers are not detected. - Compressed textures (uploaded via compressedTexImage2D) are skipped. - Textures loaded as img elements rather than blobs are not captured; geometry still exports correctly. - WebGPU is not covered. - Rendering inside a worker with a transferred OffscreenCanvas is not reachable, because content scripts do not run in workers. - Node and world transforms are lost. Buffers are in local space and the engine applies the world matrix in the shader, so a page that applies a root rotation will produce an export that imports rotated. - Material scalar factors are invisible; export assumes 1.0. - Scenes split across many meshes export the largest primitive, not the whole scene. PRIVACY MeshGrab makes no network requests of any kind. There is no server, no telemetry, no analytics, and no remote code. Captured data lives only in the memory of the tab being inspected and is discarded when that tab is closed, navigated, or reset. Nothing is written to extension storage. MeshGrab requests no host access at install. It cannot read or run on any site until you enable that site, which grants one origin at a time and can be undone from the popup or from chrome://extensions. Source, privacy policy and issue tracker: https://github.com/kmatzen/meshgrab MIT licensed.