Segmentation Options
This panel controls how different segmentation tools behave.
Active Drawing Label
This is the label with which you draw when you use the polygon tool, the paintbrush tool and various other segmentation tools in SNAP. You can select from a list of labels, or you can create your own using the label editor (see below).
Draw Over
This dropdown gives you more control over drawing. It specifies which voxels may or may not be overridden by the active drawing labels during drawing operations. When it's set to All Labels, your segmentation operations will label all voxels with the active drawing label. When set to Clear Label, segmentation operations will override only those voxels that have not already been assigned another label.