private int GetIndexAt(int row, int col)
{
var vertexIndex = _jumpIndices[row, col];
if (vertexIndex == -1)
{
_jumpIndices[row, col] = vertexIndex = _vertices.Count;
var v = _offset + new Vector3(row * _tileSize, col * _tileSize, _heightMap[row, col]);
if (_rootTransform.HasValue)
v = (Vector3)Vector3.Transform(v, _rootTransform.Value);
_vertices.Add(v);
}
return vertexIndex;
}