Undo settings

These settings control the operation of the Undo/Redo features, which are enabled or disabled with the first button. When enabled, undo and redo operations are saved in a differential, compressed, format which is designed to be reasonably fast but also memory efficient. However, when disabled, no operations are recorded at all and no additional memory is used by this process. Disabling this feature may hence slightly speed up normal operation, particularly when deleting a large amount of data (for instance an entire detailed set of object contours), and it will also reduce the memory consumption slightly (see below).

Be aware that, if you do choose to disable it, re-enabling just after you deleted something you wanted to recover will not help!

You can choose what is included in the undo/redo lists using the following selection boxes. Some typical use cases might be:

• If you are only interested in preserving any changing of object contours, just check the 'Object contour data' box.
• If you want to preserve changes you make to any editable data, check this and 'Landmark and curve data'.
• If you also want to preserve changes to object materials and volume colour mapping, check these and 'Object properties' and 'Volume display settings'.
• If you also want to include graphics and lighting settings etc, check everything except for 'General display settings'.
• Checking 'General display settings' will also preserve changes to reslices and the viewpoint in the 3D window.

It is never possible to undo/redo anything associated with the actual image data or positions of each frame, nor to undo any controls which are not resources saved with a data file.

You can set a limit on the amount of memory used by the undo list by changing the 'Memory limit' option, and you can see how much is currently being used (and whether it is currently enabled or disabled) using the 'Show memory usage' button.