At My Fingertips

Rapid Playground

In this activity we will build the following compass graphic:

The compass is a complicated graphic, we cannot approach it as a single problem: we have to decompose it in simpler graphics.

We will decompose the compass in three big components: the needle, the housing and the dial. Each of these components can and should be further decomposed!

Let's start by building the compass' needle, which should look something like this:

Since the bottom part is just a repetition of the top part, of a different color,
we should adopt **refactoring** and **extract** the part that repeats in a simpler function to be reused:
for example a function that generates half of a needle.

`half_needle`

FunctionThe `half_needle`

function should return an isosceles triangle of the wanted `height`

and `color`

,
rotated vertically like the following one:

The top angle of the triangle should measure `13`

degrees.

If you want, you can import and use the `isosceles_triangle`

function from the
Triangles
activity using your toolbox.

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`needle`

FunctionA needle is composed by a red half-needle and a white one, on top of two slightly smaller black half-needles, with a small black circle overlayed on top.

The **thickness** of the *black outline* should measure `height / 30`

,
and the **diameter** of the black circle should measure `height / 20`

.

If you want, you can import and use the `circle`

function from the
Circles
activity using your toolbox, you will find it useful further it in this activity!

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The housing of a compass is the container that holds the internal components of the compass, such as the magnetic needle.

In our case this is what the housing will look like:

The housing itself is a fairly complex graphic: we should decompose it into smaller problems!

We are going to decompose the housing in three parts: the compass rose, the background (which contains the compass rose), and the needle (which we have already implemented).

`compass_rose`

FunctionWe are going to build an approximation of a compass rose, like the following one:

As you can see it is not a perfect compass rose, but in this activity it's not needed since the needle is going to be overlayed on top of the center!

The **thickness** of the black outline should measure `diameter / 80`

,
where `diameter`

is the total diameter of the rose.

You can and should use the `half_needle`

function you implemented before!

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`housing_background`

FunctionThe background of the housing should look something like this:

Here you will find the `circle`

function very useful!

The **thickness** of the line should measure `diameter / 200`

,
and the **diameter** of the internal ring should measure `diameter / 2`

.

The **thickness** of the white part of the ring, should measure `line_thickness * 3`

.

Use the `compass_rose`

function you just implemented, to generate the compass rose contained in the ring!

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`housing`

FunctionThe housing should combine the `housing_background`

function and the `needle_function`

.

The `housing`

function takes the total `diameter`

of the housing,
and the `angle`

at which the needle should be rotated, clock-wise.

The `height`

of the needle should measure `diameter * 0.9`

.

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Let's now build the final component of the compass: the dial.

As you can see the dial graphic is very complex!

We are going to decompose it into three simpler graphics: the segments, the numbers and the cardinal points. Then, the three sould be all overlayed on top of a black circular background.

`dial_segments`

FunctionLet's start with the segments of the dial. There should be 360 `white`

segments, with a slighty longer segment for angles representing multiples of five.

The **width** of the longer segment should measure `diameter / 20`

, and it's thickness should meassure `1 / 20`

times its **width**.

The shorter segment should have a **width** of `1 / 3`

of the longer segment's, and the same **thickness**.

You can use transparent rectangles to move the segments to form the outer part of a circle.

Use pin and compose.

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`dial_numbers`

FunctionNext, let's implement the `dial_numbers`

function that should return the following graphic:

Use the pytamaro text function to generate the numbers.
It takes a string as parameter `content`

, therefore you will have to convert integer numbers to a string. For the font, use `"Roboto Condensed"`

.

To convert integers to strings you can use the python function `str(integer_value)`

, in the following way:

```
x = 7 # x has type `int`
y = str(7) # y has type `str`, and value "7"
```

The numbers should have font "Ubuntu Condensed", and points (size) of `diameter / 15`

.
The numbers `80`

, `100`

, `260`

, and `280`

should have a smaller size of `0.6`

times the bigger number's size.

The spots for numbers `0`

and `180`

should be left empty!

Use transparent rectangles again, to move the text on the outer part of a circle.

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`cardinal_points`

FunctionThe `cardinal_points`

function should generate the following graphic:

The font of the text is "Roboto Condensed", and the size of `E`

, `W`

, and `S`

should measure `diameter / 15`

.
The size of the `N`

should be `1.4`

times more.

Use transparent rectangles again, to move the text on the outer part of a circle.

Notice that the letters are not rotated, whereas the numbers were!

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`dial`

FunctionLet's generate a dial by composing the segments together with the numbers and the cardinal points, on top of a black circular background.

The cardinal points' and the numbers' `diameter`

should measure `0.9`

of the total `diameter`

.

Use the following functions you implemented before: `dial_segments`

, `dial_numbers`

, and `cardinal_points`

.

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Finally, it's time to compose the final compass!

The `compass`

function should generate a compass with the given `diameter`

,
with the needle oriented according to the given `needle_angle`

.

The **housing** should measure `3 / 4`

of the compass.

Use the `housing`

function you implemented, with the `dial`

function.

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This activity has been created by LuCE Research Lab and is licensed under CC BY-SA 4.0.

Compass

PyTamaro is a project created by the Lugano Computing Education Research Lab at the Software Institute of USI

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