Menu : TRIM

Command: Intersect:Parting Line

Shortcut : None

This command calculates the split or parting line of the target surface. The split line is calculated as the horizon of the surface when viewed from the Z direction. In other words the surface(s) are split into two pieces, one where all surface normals are pointing downwards, and another with normals pointing up. The command calculates the split line and stores the result as 3D curves. It also cuts the surface along these lines making the two halves, which can be used to make a mold. In the simple example below a torus is split in two.

The accuracy with which this calculation should be performed is requested in a parameter box as well as the joining accuracy for the resulting 3D parting line pieces. Small normal tolerances give accurate results, while a large joining accuracy may help the system to better construct the 3D parting line.As the third parameter the system asks, whether just the top or bottom part of the surfaces should be kept, or both.

In order for the system to recognize the top and bottom parts, the normal directions of the surfaces must be oriented consistently inside or outside to the model. This may most conveniently be done using command SURFACEÞNormals:Change for each inverted surface, using the single sided shading mode.

The command will have trouble computing the parting line if there are vertical walls in the model, even small ones. In such cases, the resulting parting line will typically not cut out anything of the model (the result being an open trim curve).

The system colors the resulting surfaces which were processed without problems as blue, or green. Surfaces with non-closed parting lines are colored yellow. Surfaces with other problems are colored red.