Kinematic · Spin a donut with one line of Python

Any number in Properties can follow a line of Python instead of holding still. Kinematic runs the line again on every frame, and t is the time in seconds since the graph started playing.

Steps

Click New Project. On the start card, click Add a shape and pick Torus. A donut lands in the middle of the view.
Give it a color. Open Surface > Material > New PBR material. In the Objects panel, under Materials, click Torus 1 material. In Properties, click the hex box beside Base color, type #E8833A and press Enter.
The donut with its new material, and Torus 1 material listed under Materials.
Click Torus 1 in the Objects panel so Properties shows the donut. Under Configuration, type turn in the filter box. Turn X, Turn Y and Turn Z are left.
Right-click Turn X and choose Set Python Driver (@). The Driver Editor opens in Python mode, with t already in the Expression box.
Right-click a setting for its driver choices. Set Python Driver (@) is the second one.
Replace t with this line and click OK:
python
```
(t * 90) % 360
```
The donut tumbles a quarter turn every second. The % 360 wraps the angle back to 0 after a full turn, because Turn X takes values from -360 to 360.
The Driver Editor in Python mode. It checks the line as you type and shows the value it gives right now.
Look at Turn X in Properties. It now shows the value changing live, the line it follows, and a small graph of the last few seconds.
Turn X follows the Python line. Turn Y and Turn Z still hold plain numbers.
Make it breathe. Type uniform in the filter box, right-click Uniform scale, choose Set Python Driver (@), and replace t with:
python
```
1 + 0.2 * sin(t * 4)
```
Click OK. The donut swells and shrinks a little, about every second and a half.
Uniform scale follows a sine wave between 0.8 and 1.2.
Hover over the viewport and press Shift+H to hide the handles, then watch it move. Save with File > Save.

On the canvas

The steps added a 3DGeoTorus for the donut and a PbrMaterial that a 3DGeoSetMaterial puts on it. The two Python lines live on the torus itself, as the values of its turn and size settings.

Make it yours

Bob it up and down: filter for move, right-click Move Y and set its Python driver to 0.5 * abs(sin(t * 3)).
Add a second turn with Turn Y set to (t * 40) % 360, so it wobbles as it tumbles.
Slow it down: (t * 30) % 360 turns it once every twelve seconds.
math is ready to use in any line, so math.floor(t) * 45 % 360 turns the donut in steps, once a second.

If it goes wrong

The editor says the line is not valid: check the brackets, and use t (not time) for the seconds.
To go back to a plain number, right-click the setting and choose Set Constant Value.

Spin a donut with one line of Python

Steps

On the canvas

Make it yours

If it goes wrong

Free and open. Yours, forever.