Outlines are objects drawn on photos to trace a flat shape or pattern. An Outline can be drawn on a single photo, or it can span across multiple photos. Outlines are like Surface Draw objects (see Surface Drawing) in that they are defined by points drawn on a single photo and use an associated 3D surface to obtain their position in 3D, and do not need to be referenced.
Compared to Surface Draw, Outlines are more CAD-like – the shapes that are drawn are smoother and easier to draw (e.g., with repeatable Fillet radius settings). In addition, Outlines blur the line between what is 2D on a photo, and what is 3D – this is to simplify the process of outlining objects across many photos.
Outlines can only be drawn with an associated Plane surface (see also Creating Planes). Outlines are made up of one or more Outline Parts.
See also Outline Defining/Modifying.