Fig. 3. Example of a 3D ground truth particle structure. (a) A text snippet from the.JSON structure file, showing how particle
sizes (“size”) and coordinates (“x”, “y”, and “z”) are represented. (b) A 3D rendering of a particle structure, which would be used to create a synthetic 2D SEM image as described in the text. The x-axis is shown by the red arrow; the y-axis is the green arrow; and the z-axis is the blue arrow. The imaging plane is located at z¼0, and is shown by the overlaid grid.