glimpse

A Windows Shell Extension that shows thumbnail previews of 3D model files directly in File Explorer. Supports glTF/GLB, Wavefront OBJ, Blockbench, Minecraft Java/Bedrock, and Vintage Story formats.

Supported Formats

Format	Extensions	Description
glTF / GLB	.gltf, .glb	Industry-standard 3D transmission format
Wavefront OBJ	.obj	Widely supported 3D model format with .mtl material support
Blockbench	.bbmodel	Blockbench model format used for Minecraft modding and more
Minecraft Bedrock	.json	Bedrock Edition geometry format (minecraft:geometry)
Minecraft Java	.json	Java Edition block/item model format
Vintage Story	.json	JSON-based model format used by Vintage Story

JSON Format Detection

Multiple formats share the .json extension. glimpse identifies them by unique content markers:

Format	Detection Key
Blockbench	.bbmodel extension, or "meta" + "format_version" in content
Minecraft Bedrock	"minecraft:geometry" key
Minecraft Java	"parent" field (e.g. "block/block") with "elements"
Vintage Story	"elements" with cube faces and "from"/"to" (fallback)

Features

• Native Explorer Integration — Thumbnails appear just like images, videos, and other supported formats
• Texture Support — Renders embedded textures (glTF, Blockbench), companion .mtl textures (OBJ), and asset tree textures (Vintage Story)
• Vertex Colors — Displays models with vertex color attributes (glTF)
• Material Colors — Reads diffuse colors from .mtl materials (OBJ)
• Asset Tree Resolution — Vintage Story models resolve textures from the assets/*/textures/ directory hierarchy
• Multiple Formats — 7 format variants across 4 file extensions
• Software Rendering — No GPU required, works in VMs and remote desktop
• Lenient Parsing — Gracefully handles files with missing textures by rendering geometry with solid color

Screenshot

Models shown are from FrenchKrab/mc-blockbench-models.

How It Works

glimpse is a COM DLL implementing Windows' IThumbnailProvider interface. When Explorer encounters a supported model file:

1. Windows loads our DLL and passes the file data
2. We auto-detect the format (by extension and content analysis) and parse the model
3. A software rasterizer renders the scene with:
   • Automatic camera framing based on bounding sphere
   • Flat shading with ambient + diffuse + specular lighting
   • Z-buffer depth testing
   • Per-pixel texture sampling with barycentric UV interpolation
4. The resulting bitmap is returned to Explorer

Format-Specific Details

• glTF/GLB — Parsed via the gltf crate. Supports embedded textures, vertex colors, and scene graph traversal.
• Wavefront OBJ — Parsed via obj-rs. Loads companion .mtl files for diffuse colors (Kd) and textures (map_Kd). Handles N-gon faces via fan triangulation.
• Blockbench — Parsed via serde_json. Supports embedded base64 textures, element hierarchy, and both Java Block and Free/Bedrock rotation orders.
• Minecraft Bedrock — Bone-based hierarchy with pivot rotations. Cubes use origin/size with per-face UV objects supporting uv_size mirroring and uv_rotation.
• Minecraft Java — Elements with from/to bounds and single-axis rotation. UV space defined by texture_size (default 16x16).
• Vintage Story — JSON5 with comments. When loaded from a VS asset tree, resolves textures from assets/*/textures/ directories, preferring the same domain. Supports textureSizes for per-texture UV normalization.

Installation

Download glimpse-setup.exe from the releases page and run it. See INSTALLER.md for details.

Building from Source

Prerequisites: Rust with stable-x86_64-pc-windows-msvc toolchain.

cargo build --release

This produces target/release/glimpse.dll.

CLI Testing Tool

A command-line tool is included for testing format support without installing the shell extension:

cargo build --release
target/release/glimpse-cli.exe model.gltf 256

This renders a 256x256 thumbnail and saves it as a PNG next to the input file.

Limitations

Limitation	Description
Triangles Only	Line, point, and strip primitives are skipped
No Animation	Static pose only (no skinning, morphs, or animation)
External Resources	glTF files referencing external .bin render geometry only
CPU Rendering	Fast for thumbnails but not real-time

Dependencies

• gltf — glTF 2.0 parsing
• obj-rs — Wavefront OBJ/MTL parsing
• serde / serde_json — JSON parsing for Blockbench and Minecraft formats
• json5 — Vintage Story JSON5 parsing
• glam — Math library for matrix/vector operations
• base64 — Data URI decoding
• image — PNG/JPEG texture decoding
• windows — Windows API bindings

Contributing

Contributions welcome! Please open an issue or PR.

License

MIT License — see LICENSE for details.