Exploring 3D space with a computer - Part 2: a set of solids
Adrian Oldknow
Reflection Continued
Using the Pyramid tool from the eighth icon we create the pencil point using the top hexagon and the point F . Check out the effects of sliding F or E . You can download the file 
Pencil.cg3
When you first create a prism or pyramid it will be completely `covered in' by having all its faces coloured in the same way. With the `Pencil.cg3' file opened in Cabri 3D move the cursor slowly towards one of the prisms until you see the message `this convex polyhedron'. Then right-click to see the menu associated with this shape. Find the item called `Surface style' and select one of the options, such as `Small Hatches'. This way you can see through the object while you are still working on your model. You can always change it back to `Solid' later.
The next model shows some of other utilities for building common solid shapes. The green `brick' uses the `XYZ Box' tool. Points A and B are taken in the ground plane, and C is on the perpendicular through B . The two points A, C define one of the long diagonals of the box.
The yellow `wedge' uses the `Tetrahedron' tool with points D,E,F in the ground plane and H on the perpendicular through G .
The blue `cage' uses the `Polyhedron' tool with the six points L,M,N,O,P,Q - with one repeated to `verify' the shape.
You can drag the points around on the model below or download the file Polyhedra.cg3
