MAPaint Technical Report:
Digital Sectioning

Digital Sectioning

Paint has been developed to define arbitrary 3D domains within a grey-level voxel image. In many cases it is convenient to define a large structure for later sub-division. In many cases the sub-division can be acheived by a planar cut or ``digital knife''. In pain this has been implemented by using a particular section view as the knife and the user can select which of the previously defined domains should be cut. The algorithm in terms of the woolz binary images is very straightforward. The 3D domain is defined by a set of intervals which can be wholey on one side of the section or cut by it. To establish this the end points of each interval are transformed using equation 5 and the resulting z' values compared with the section distance d. If both values are greater than d then the interval is part of the object on one side, if both values are smaller then the interval is part of the object on the other side and if one is larger d and the other smaller then the interval must be split into two parts. The dividing point is proportional to the respective distances from each end point.

Dividing a volume defined in terms of intervals is very efficient and the time is proportional to the number of intervals which scales as the number of planes times the number of lines.