OpenCTM: Open File Format for Compressed 3D Meshes

OpenCTM (I guess OpenCTM means Open Compressed Triangle Mesh) is a file format for storing 3D triangle meshes in a compact and versatile format. The format supports per-vertex position, normal, texture coordinates and custom attributes. Large geometries up to billions of triangles and vertices can be stored (OpenCTM uses 32-bit face indices). The OpenCTM SDk is open source and written in C.

You can download the OpenCTM SDK HERE.

Here is how to load a ctm file:

#include 
CTMcontext context;
CTMuint  vertCount, triCount, * indices;
CTMfloat  * vertices;

 // Create a new context
 context = ctmNewContext(CTM_IMPORT);

 // Load the OpenCTM file
 ctmLoad(context, "mymesh.ctm");
 if(ctmGetError(context) == CTM_NONE)
 {
    // Access the mesh data
    vertCount = ctmGetInteger(context, CTM_VERTEX_COUNT);
    vertices = ctmGetFloatArray(context, CTM_VERTICES);
    triCount = ctmGetInteger(context, CTM_TRIANGLE_COUNT);
    indices = ctmGetIntegerArray(context, CTM_INDICES);

    // Deal with the mesh (e.g. transcode it to our 
    // internal representation) 
    // ...
 }

 // Free the context
 ctmFreeContext(context);

and here is how to create a ctm file from your geometry.

#include 
CTMcontext context;
CTMuint  vertCount, triCount, * indices;
CTMfloat  * vertices;

// Create our mesh in memory
vertCount = 100;
triCount = 120;
vertices = (CTMfloat*)malloc(3*sizeof(CTMfloat)*vertCount);
indices = (CTMuint*)malloc(3*sizeof(CTMuint)*triCount);
// ...

// Create a new context
context = ctmNewContext(CTM_EXPORT);

// Define our mesh representation to OpenCTM (store 
// references to it in the context)
ctmDefineMesh(context, 
                       vertices, 
                       vertCount, 
                       indices, 
                       triCount, 
                       NULL);

// Save the OpenCTM file
ctmSave(context, "mymesh.ctm");

// Free the context
ctmFreeContext(context);

// Free our mesh
free(indices);
free(vertices);

I’ll try to add it in GeeXLab…