protected void WritePoseVertex( BinaryWriter writer, int vertexId, Vector3 offset )
{
long start_offset = writer.Seek( 0, SeekOrigin.Current );
WriteChunk( writer, MeshChunkID.PoseVertex, 0 );
WriteInt( writer, vertexId );
WriteVector3( writer, offset );
long end_offset = writer.Seek( 0, SeekOrigin.Current );
writer.Seek( (int)start_offset, SeekOrigin.Begin );
WriteChunk( writer, MeshChunkID.PoseVertex, (int)( end_offset - start_offset ) );
writer.Seek( (int)end_offset, SeekOrigin.Begin );
}