This illustrates modelling of growth sectors in an intergrowth.
After generating the Carlsbad twin in example 2, select Save/Recover Orientation in the Rotation menu, and select the Recover original orientation button. Then select Cartesian Axes in the Rotation menu to rotate 90 degrees on z. This should give a view down the b axis.
Now select Sections/Growth Zones from the Input1 menu. Click on the Growth Zones radio button, and then on the Zone Settings button. In the Growth-Zone Settings dialog, click on the Linear button, and enter 10 in the number of zones box. Check the Sector boundaries box.
Remove the dialogs by clicking on OK, then select Display from the Modes menu, and set the display mode to Sections/Zones. The drawing will be replotted automatically.
Most of the growth sectors can be assigned to one face or two faces belonging to one or the other of the two individuals in the twin. The exception is the middle sector of the three bounded by 110 faces - actually, what is shown in this plot is the boundary between the (110) and (1-10) sectors of one individual and the (-110) and (-1-10) sectors of the other. There are thus four "combined" sectors, in which (110) of one individual is coincident with (-110) of the other, etc. These combined sectors may be illustrated more clearly in the normal three-dimensional view of the twin by switching Edges in faces in the Preferences dialog (Settings menu) on. Although the two coincident faces in each sector belong to the same form, they are not in the same orientation, so these "combined" sectors can not exist in reality. Presumably in a real twin the non-combined sectors above and below are extended to squeeze out the combined sectors, forming an irrational line of junction across the 110 faces.