Exploring 3D space with a computer – Part 3: building models from plans
Adrian Oldknow
Bringing Solids To Life
To finish this instalment we will take a quick look at making nets of simple solids and bringing them to life. The inspiration for this comes from the Year 4 BBC TV Maths Channel programme on shapes shown last October & November. This has examples of buildings from Legoland, and shows how to build up solid shapes from nets using CAD software for packing from Gencia: http://www.thisisgencia.com/ .
The figure shows a fold-up net of a cube used as the inner packaging for a jar of cosmetics. Any net for a cube will need to consist of six squares, but not all arrangements of six squares will fold up to form a cube.
Investigation : how many different nets of a cube can you find?
The shape we'll work on in this section is a triangular prism - you may be familiar with the yellow packaging for some sweet Swiss chocolate bars! Here is a Cabri 3D prism.
It was built by first constructing a vertical equilateral triangle defined by points O and A .
The point D can slide on a line (hidden) perpendicular to AB at A in the ground plane, and this defines the vector AD . The prism is the `product' of the triangle and the vector. You can download the above file 
prism.cg3.
Can you imagine what shape each of the five faces of this solid must look like?
Can you sketch a possible net for this solid? How many folds will we need?
Here is my attempt at a net for the triangular prism. Did you get something similar?
You can download the file as prism-net.cg3 .
