Generating Convex Hulls from ROIs

Dragonfly lets you generate convex hulls as filled regions of interest, outer shell ROIs, or as meshes.

Convex hulls are calculated from the minimum set of points that define a polygon containing all of the labeled voxels of a region of interest or all of the labeled voxels of each connected component in a multi-ROI. If you imagine the points as pegs on a board, you can find the convex hull by surrounding the pegs by a loop of string and then tightening the string until there is no more slack.

In the illustration below, a convex hull was generated from a region of interest describing a number of particles.

Original ROI (on left) and generated convex hull as a filled ROI (on right)

Convex hull types

Type	Description
Filled ROI	Generates a convex hull as a filled region of interest for the selected ROI.
Outer Shell ROI	Generates a convex hull as an outlined region of interest for the selected ROI.
Mesh	Generates a convex hull as a mesh for a selected ROI, as shown below. Convex hull as a mesh

1. Right-click the required ROI in the Data Properties and Settings panel.
2. Choose Generate Convex Hull As in the pop-up menu and then the type of convex hull you want to generate.

   The Binning dialog appears.

3. Select a Binning factor within the range of 1 to 8, as required.

   Note Binning is the downsampling factor used when generating the space where the convex hull is created prior to its re-projection in the initial space.

4. Click OK to generate the convex hull.