When defining several VOIs, the user may want to control whether they can overlap, or not. To this end, the editing can be set to one of three different modes as illustrated below.
Their effect is as follows.
No control of VOI overlapping, contours can intersect arbitrarily.
Trim new/modified VOIs along existing VOIs. The existing VOIs have priority. The new VOI is modified by removing any intersection area with the existing VOIs.
Trim existing VOI along new/modified VOIs. The new VOI has priority. The existing VOIs are modified by removing any intersection area with the new VOI.
The example below illustrates the effect when shifting the green ellipse left in the different control modes.