Gets all points and angles on the path of an archimedean spiral. The distance between two points is almost constant.

It returns a vector of `[[x, y], angle]`

.

An `init_angle`

less than 180 degrees is not recommended because the function uses an approximate approach. If you really want an `init_angle`

less than 180 degrees, a larger `arm_distance`

is required. To reduce the error value at the calculated distance between two points, you may try a smaller `point_distance`

.

## Parameters

`arm_distance`

: If any ray from the origin intersects two successive turnings of the spiral, we'll have two points. The`arm_distance`

is the distance between these two points.`init_angle`

: In polar coordinates`(r, θ)`

Archimedean spiral can be described by the equation`r = bθ`

where`θ`

is measured in radians. For being consistent with OpenSCAD, the function here use degrees. The`init_angle`

is which angle the first point want to start.`point_distance`

: Distance between two points on the path.`num_of_points`

: How many points do you want?`rt_dir`

:`"CT_CLK"`

for counterclockwise.`"CLK"`

for clockwise. The default value is`"CT_CLK"`

.

## Examples

```
use <polyline2d.scad>;
use <archimedean_spiral.scad>;
points_angles = archimedean_spiral(
arm_distance = 10,
init_angle = 180,
point_distance = 5,
num_of_points = 100
);
points = [for(pa = points_angles) pa[0]];
polyline2d(points, width = 1);
```

```
use <archimedean_spiral.scad>;
points_angles = archimedean_spiral(
arm_distance = 10,
init_angle = 180,
point_distance = 5,
num_of_points = 100
);
for(pa = points_angles) {
translate(pa[0])
circle(2);
}
```

```
include <archimedean_spiral.scad>;
t = "3.141592653589793238462643383279502884197169399375105820974944592307816406286";
points = archimedean_spiral(
arm_distance = 15,
init_angle = 450,
point_distance = 12,
num_of_points = len(t)
);
for(i = [0: len(points) - 1]) {
translate(points[i][0])
rotate(points[i][1] + 90)
text(t[i], valign = "center", halign = "center");
}
```