# Vertical control points

The panorama tools optimizer understands various different schemes for
aligning photos using control points:
Normal points are **t0** points, horizontal control points are **t1** points and
vertical control points are **t2** points.

The main use of **vertical control points** is to change the perspective of the output panorama such that the marked structures are vertical in the output projection. In a multi image panorama this is only possible if the optimization of Roll and Pitch is allowed for all images and of Yaw for all but the anchor image.

You set **vertical control points** on a vertical structure as far apart from each other as possible.

Please note that all real world vertical lines only stay vertical in rectilinear, cylindrical and equirectangular projections. In fisheye projection only the vertical line through the image center stays vertical.

More details in Perspective correction and Panotools internals