- The x-y-z co-ordinates of each vertex of the model are calculated in an Excel spreadsheet. Within the spreadsheet these co-ordinates are simple functions of the five parameters shown in the diagram, derived using basic trigonometry. Changing the values of any of the four parameters creates modified models.
- The spreadsheet is saved as a text file, consisting of a sequence of x-y-z co-ordinate locations, together with a fourth value (c) indicating the how the successive vertices should be joined.
- This text file is used by the program Rotater to produce rotatable wireframe models.
- A succession of views from Rotater are then saved (using AppleScript routines included with Rotater 3.5) and joined together as an animated GIF (using the shareware program GifBuilder).
- Rotater is a shareware program produced by Craig Kloeden for the Apple MacIntosh that "reads a set of 3-dimensional points and lines and plots them in a window. The image can then be rotated with the mouse in real time". It is a very convenient program for visualising 3D data, although of course it is essential that you can mathematically describe an object before you can use it.
- Windows equivalent - Rotate this is a Windows version of Rotater. I do not know how well it works, but to help here are zippped versions of my files.
- Rotater files for the rhomboaster models are available here (N.B. they are of no use without the Rotater program).
- The Excel spreadsheet used to calculate them is available here (N.B. You need to save this link as source then open from inside Excel).
- Other examples of coccoliths and nannoliths modelled with this program are available elsewhere on the INA site.

The figure below illustrates the morphological model used to construct all the drawings shown on the main page. The practical process of model construction is:

rhomb | cuspis | bramlettei | calcitrapa | contortus | |

Nannolith thickness | 10 | 10 | 10 | 10 | 10 |

Central body radius | 10 | 10 | 10 | 10 | 10 |

Ray angle | 15 | 15 | 20 | 20 | 15 |

Ray length | 11.5 | 15 | 30 | 60 | 30 |

Interlayer angle | 60 | 60 | 60 | 60 | 30 |

Note that not all parameters were varied. In particular for the rhomb->

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