# Polyhedrons

## 3-D figures formed by polygons enclosing regions in space.

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Roly Poly Polyhedron!

Stella is the name of a computerized polyhedron creator. Designed by Robert Webb of Australia, the program allows you to create a polyhedron on the screen and print out its net, which you can then cut out and assemble into a real-life 3D model of your original creation. The Stella software contains a built-in polyhedron library that includes all the Platonic solids, or regular polyhedrons, as well as many other shapes.

#### Why It Matters

Polyhedrons are classified according to the number of faces they have. Sometimes you need to know how many edges and vertices a polyhedron has as well. Counting the number of faces, vertices, and edges can be very difficult when dealing with the two-dimensional pictures you see in textbooks and on the computer screen. Oftentimes, one or more face, vertex, and/or edge can be hidden behind another.

For example, if you only had the above picture of the icosahedron to rely on, you might assume that this polyhedron had eight faces because that’s all you can count. But the icosahedron actually has twelve additional faces that can’t be seen from this angle of the image. Stella enables you to actually hold a polyhedron in your hand to make an accurate count.

Take a look: http://www.software3d.com/Stella.php

#### Explore More

Check out the following video to see Stella in action.

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