void ProgressiveMeshGenerator::addIndexData(IndexData* indexData, bool useSharedVertexLookup, unsigned short submeshID)
{
    const HardwareIndexBufferSharedPtr& ibuf = indexData->indexBuffer;
    size_t isize = ibuf->getIndexSize();
    mIndexBufferInfoList[submeshID].indexSize = isize;
    mIndexBufferInfoList[submeshID].indexCount = indexData->indexCount;
    if (indexData->indexCount == 0) {
        // Locking a zero length buffer on linux with nvidia cards fails.
        return;
    }
    VertexLookupList& lookup = useSharedVertexLookup ? mSharedVertexLookup : mVertexLookup;

    // Lock the buffer for reading.
    char* iStart = static_cast<char*>(ibuf->lock(HardwareBuffer::HBL_READ_ONLY));
    char* iEnd = iStart + ibuf->getSizeInBytes();
    if (isize == sizeof(unsigned short)) {
        addIndexDataImpl<unsigned short>((unsigned short*) iStart, (unsigned short*) iEnd, lookup, submeshID);
    } else {
        // Unsupported index size.
        OgreAssert(isize == sizeof(unsigned int), "");
        addIndexDataImpl<unsigned int>((unsigned int*) iStart, (unsigned int*) iEnd, lookup, submeshID);
    }
    ibuf->unlock();
}