Developing better products faster

A module for MacroPac, shipped automatically with each release, is the Custom ShapeBuilder, which lets you create specific shape to your own design. The shapes are read into MacroPac so they can then be packed using one of the static or shake pack options.

The custom shapes are built up from spheres, and specifying them is easy. Simply add a sphere of the desired radius, then add more spheres to it. By defining the distances between the spheres and the angles between them, custom shapes are created quickly. Shapes like triangles, tetrahedra, and octahedra - even shapes like tubes and rings - can be defined and built in minutes. Shapes can be stored, retrieved and edited, allowing you to create your own personal library of custom objects.

Let's look at a frivolous example - making letters of the alphabet. Shapes like H and T are straightforward, but even more complex shapes are possible, as we've shown here.

Depending on the simulation you plan, shapes can be built as 2D or 3D objects. For a 2D object, the 'volume' is simply the sum of the areas of the component circles, while for 3D objects, the ShapeBuilder sums the volumes of the spheres. These may underestimate the real volumes, so the object volume is user-editable. Alternatively, you can simply accept the calculated value.

If we build 2D 'letters' and pack these into a 2D box with hard boundaries, using the static pack option, then we get a plate of alphabet soup, as shown.

3D objects in a 3D box are also possible - in this case, we have displayed cubes instead of the component spheres, to show more clearly the object to which each sphere belongs. Here, we have used the shake pack option in MacroPac, together with several iterations of the settling algorithm, to try to achieve maximum packing. Even so, the packing fraction is only on the order of 10% showing that, for relatively spiky structures like the objects with four and six 'arms' given here, a relatively open structure is obtained. For some examples - for example, when you want relatively unobstructed flow through the structure - then these objects may be desirable shapes.

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