When filleting two Outlines, you click select near the ends of those Outlines that you want to be filleted. The other possible ends are not checked for compatibility. When the filleting request is invalid (e.g., between incompatible ends, ends or lines are too parallel, radius is too big, etc.) a warning will appear, and a straight dashed line will appear on the photos between the chosen ends. When the error dialog is accepted by pressing on the “Remove Fillet” button, the fillet attempt (and the thin dashed line) will be removed. In the case where a fillet becomes invalid after it was created (e.g., the radius was changed past the maximum, or points were dragged to make ends too parallel), the fillet object remains and appears on photos as a straight fine-dashed line between the end points, and appears on the Outline table as ‘not 3D’ (an if not 3D, it will not be exported).
Once a Fillet connects two Outlines, they become one Outline object. For example, if two Outline Lines are connected by a Fillet, the connected Lines becomes one Outline (of three parts). See the screen captures in Fillet Examples.
Note that you can use a fillet to close an Outline. If an Outline has one remaining open gap, and the two ends are filletable (not parallel, etc.), then you can select a single Outline and press the Fillet tool to close the Outline with a single fillet.
Outline objects that are being filleted can be modified to shorten or lengthen. For example, two Lines being filleted that are too long for the given radius will be cut back so the fillet fits. The Lines are not permanently modified (as PhotoModeler is a parametric editor). If you delete the fillet, the full-length lines will return. Objects can also be extended to meet the fillet of a given radius. Lines, Splines and Arcs are all extended by straight lines.
Fillets are parametric in that if you modify one of the objects that a fillet is connected to (drag a point, add, or delete a point, etc.), the attached fillet updates as well. This happens in real time. The fillet radius can also be changed at any time in the Properties.