![example picture for normal()](/images/reference/Sketch_normal_0.png)
```python
def setup():
py5.size(100, 100, py5.P3D)
py5.no_stroke()
py5.background(0)
py5.point_light(150, 250, 150, 10, 30, 50)
py5.begin_shape()
py5.normal(0, 0, 1)
py5.vertex(20, 20, -10)
py5.vertex(80, 20, 10)
py5.vertex(80, 80, -10)
py5.vertex(20, 80, 10)
py5.end_shape(py5.CLOSE)
```