Dynamic VBOs

    // USAGE style 2
    // Reusing one vertex buffer for multiple objects
 
    // Determine the size of data to be moved into the vertex buffer.
    UINT nSizeOfData = nNumberOfVertices * m_nVertexStride;
 
    // No overwrite will be used if the vertices can fit into 
    //   the space remaining in the vertex buffer.
    DWORD dwLockFlags = D3DLOCK_NOOVERWRITE;
    
    // Check to see if the entire vertex buffer has been used up yet.
    if( m_nNextVertexData > m_nSizeOfVB - nSizeOfData )
    {
        // No space remains. Start over from the beginning 
        //   of the vertex buffer.
        dwLockFlags = D3DLOCK_DISCARD;
        m_nNextVertexData = 0;
    }
    
    // Lock the vertex buffer.
    BYTE* pBytes;
    if( FAILED( m_pVertexBuffer->Lock( (UINT)m_nNextVertexData, nSizeOfData, 
               &pBytes, dwLockFlags ) ) )
        return false;
    
    // Copy the vertices into the vertex buffer.
    memcpy( pBytes, pVertices, nSizeOfData );
    m_pVertexBuffer->Unlock();
 
    // Render the primitives.
    m_pDevice->DrawPrimitive( D3DPT_TRIANGLELIST, 
               m_nNextVertexData/m_nVertexStride, nNumberOfVertices/3)
 
    // Advance to the next position in the vertex buffer.
    m_nNextVertexData += nSizeOfData;