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OpenCTM is a file format designed to store compact 3D triangular meshes. It comes with a library for developers and 3D designers to read and write OpenCTM files.

OpenCTM only handles triangular mesh data and is not a scene description format. It is adaptable to almost any application, allowing visualization systems, game engines, medical applications to customize their own scene description or model format using OpenCTM as a 3D data support format.

The file format (extension .ctm) has the following features:

  • Open format (zlib/libpng license).
  • Supports storage of per-vertex normals, UV coordinates, and custom vertex attributes.
  • Can store very large geometries (billions of triangles and vertices).
  • Compact storage of 3D triangular geometries, using entropy reduction techniques, combined with state-of-the-art entropy coding (LZMA). An STL file can typically be compressed to 5-6% of its original size.
  • Lossless compression with user-controllable precision:
    • Lossless compression (IEEE 754 32-bit floating point).
    • Fixed-point representation with user-controllable precision

The included 3D file converter (ctmconv) has the following features:

  • Supports the following formats (read and write)::
    • OpenCTM (.ctm)
    • COLLADA 1.4/1.5 (.dae)
    • Stéréolithographie (.stl
    • Format triangle de Stanford (.ply)
    • Studio 3D (.3ds)*
    • Géométrie du front d'onde (.obj)*
    • Objet LightWave (.lwo)
    • Objet Geomview (.off)
  • Control over OpenCTM compression settings.
  • Scaling and transformation.
  • Multiplatform: Windows, Mac OS X, Linux, OpenSolaris, etc.

The visualization application (ctmviewer) has the following features:

  • Interactive OpenGL 3D view:
    • Phong shading based on GLSL
    • Texturing
    • Vertex colors
  • Fast loading - perfect for previewing 3D files.
  • Imports and exports files supported by the conversion tool.
  • Portable (works on Windows, Mac OS X, Linux, OpenSolaris, etc.).

CAD Interop distributes several software solutions for preparing, viewing, and converting OpenCTM files. Below is a list of our solutions compatible with the OpenCTM format:

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