# Hello Friend.

Here is an example to demonstrate the principle of building models in zencad.

```
from zencad import *
a = box(200, 200, 200, center = True)
b = sphere(120)
c = sphere(60)
model = a - b + c
display(model)
show()
```

## What's happening:

```
from zencad import *
```

In the first line, we import into the current zencad namespace. In this case, we are interested in the `box`

,`sphere`

, `display`

,`show`

functions.

```
a = box(200, 200, 200, center = True)
b = sphere(120)
c = sphere(60)
```

Preparing geometric primitives. A box object is created with dimensions 200x200x200 and an offset of the geometric center to the origin. It also creates two spheres with a radius of 120 and 60.

```
model = a - b + c
```

Computing the model using boolean operations. First, a large sphere will be subtracted from the cube. Then a small one was added. The order of the terms is important in this case, since the operations of union and difference of geometric bodies are non-commutative.

```
disp(model)
```

The `disp`

function passes the object into the scene for later display.

```
show()
```

Displaying the scene widget.