# 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.

## If everything went well: 