https://github.com/PixarAnimationStudios/OpenSubdiv/blob/master/tutorials/osd/tutorial_0/osd_tutorial_0.cpp

//------------------------------------------------------------------------------
// Tutorial description:
//
// This tutorial demonstrates the manipulation of Osd Evaluator and
// BufferDescriptor.
//

#include <opensubdiv/far/topologyDescriptor.h>
#include <opensubdiv/far/stencilTableFactory.h>
#include <opensubdiv/osd/cpuEvaluator.h>
#include <opensubdiv/osd/cpuVertexBuffer.h>

#include <cstdio>
#include <cstring>

//------------------------------------------------------------------------------
// Cube geometry from catmark_cube.h
static float g_verts[24] = {-0.5f, -0.5f,  0.5f,
                             0.5f, -0.5f,  0.5f,
                            -0.5f,  0.5f,  0.5f,
                             0.5f,  0.5f,  0.5f,
                            -0.5f,  0.5f, -0.5f,
                             0.5f,  0.5f, -0.5f,
                            -0.5f, -0.5f, -0.5f,
                             0.5f, -0.5f, -0.5f};

static int g_nverts = 8,
           g_nfaces = 6;

static int g_vertsperface[6] = { 4, 4, 4, 4, 4, 4 };

static int g_vertIndices[24] = { 0, 1, 3, 2,
                                 2, 3, 5, 4,
                                 4, 5, 7, 6,
                                 6, 7, 1, 0,
                                 1, 7, 5, 3,
                                 6, 0, 2, 4  };

using namespace OpenSubdiv;

static Far::TopologyRefiner const * createTopologyRefiner(int maxlevel);

//------------------------------------------------------------------------------
int main(int, char **) {

    int maxlevel=2,
        nCoarseVerts=0,
        nRefinedVerts=0;

    //
    // Setup phase
    //
    Far::StencilTable const * stencilTable = NULL;
    { // Setup Far::StencilTable
        Far::TopologyRefiner const * refiner = createTopologyRefiner(maxlevel);

        // Setup a factory to create FarStencilTable (for more details see
        // Far tutorials)
        Far::StencilTableFactory::Options options;
        options.generateOffsets=true;
        options.generateIntermediateLevels=false;

        stencilTable = Far::StencilTableFactory::Create(*refiner, options);

        nCoarseVerts = refiner->GetLevel(0).GetNumVertices();
        nRefinedVerts = stencilTable->GetNumStencils();

        // We are done with Far: cleanup table
        delete refiner;
    }

    // Setup a buffer for vertex primvar data:
    Osd::CpuVertexBuffer * vbuffer =
        Osd::CpuVertexBuffer::Create(3, nCoarseVerts + nRefinedVerts);

    //
    // Execution phase (every frame)
    //
    {
        // Pack the control vertex data at the start of the vertex buffer
        // and update every time control data changes
        vbuffer->UpdateData(g_verts, 0, nCoarseVerts);


        Osd::BufferDescriptor srcDesc(0, 3, 3);
        Osd::BufferDescriptor dstDesc(nCoarseVerts*3, 3, 3);

        // Launch the computation
        Osd::CpuEvaluator::EvalStencils(vbuffer, srcDesc,
                                        vbuffer, dstDesc,
                                        stencilTable);
    }

    { // Visualization with Maya : print a MEL script that generates particles
      // at the location of the refined vertices

        printf("particle ");
        float const * refinedVerts = vbuffer->BindCpuBuffer() + 3*nCoarseVerts;
        for (int i=0; i<nRefinedVerts; ++i) {
            float const * vert = refinedVerts + 3*i;
            printf("-p %f %f %f\n", vert[0], vert[1], vert[2]);
        }
        printf("-c 1;\n");
    }

    delete stencilTable;
    delete vbuffer;
}

//------------------------------------------------------------------------------
static Far::TopologyRefiner const *
createTopologyRefiner(int maxlevel) {

    // Populate a topology descriptor with our raw data

    typedef Far::TopologyDescriptor Descriptor;

    Sdc::SchemeType type = OpenSubdiv::Sdc::SCHEME_CATMARK;

    Sdc::Options options;
    options.SetVtxBoundaryInterpolation(Sdc::Options::VTX_BOUNDARY_EDGE_ONLY);

    Descriptor desc;
    desc.numVertices = g_nverts;
    desc.numFaces = g_nfaces;
    desc.numVertsPerFace = g_vertsperface;
    desc.vertIndicesPerFace = g_vertIndices;

    // Instantiate a FarTopologyRefiner from the descriptor
    Far::TopologyRefiner * refiner =
        Far::TopologyRefinerFactory<Descriptor>::Create(desc,
            Far::TopologyRefinerFactory<Descriptor>::Options(type, options));

    // Uniformly refine the topolgy up to 'maxlevel'
    refiner->RefineUniform(Far::TopologyRefiner::UniformOptions(maxlevel));

    return refiner;
}

//------------------------------------------------------------------------------