Extrudes a 2D shape along a helix path.

When using this module, you should use points to represent the 2D shape. If your 2D shape is not solid, indexes of triangles are required. See sweep for details.

Its `$fa`

, `$fs`

and `$fn`

parameters are consistent with the `cylinder`

module.

## Parameters

`shape_pts`

: A list of points represent a shape. See the example below.`radius`

: The radius of the cylinder. The radius of the cylinder. It also accepts a vector`[r1, r2]`

.`r1`

is the bottom radius and`r2`

is the top radius of a cone.`levels`

: The level count is performed every 360 degrees.`level_dist`

: The distance between two vertial points.`vt_dir`

:`"SPI_DOWN"`

for spiraling down.`"SPI_UP"`

for spiraling up. The default value is`"SPI_DOWN"`

.`rt_dir`

:`"CT_CLK"`

for counterclockwise.`"CLK"`

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

.`twist`

: The number of degrees of through which the shape is extruded.`scale`

: Scales the 2D shape by this value over the length of the extrusion. Scale can be a scalar or a vector.`triangles`

:`"SOLID"`

(default),`"HOLLOW"`

or user-defined indexes. See sweep for details.`$fa`

,`$fs`

,`$fn`

: Check the cylinder module for more details.

## Examples

```
use <helix_extrude.scad>;
shape_pts = [
[5, -2],
[5, 2],
[4, 2],
[4, 0],
[-4, 0],
[-4, 2],
[-5, 2],
[-5, -2]
];
helix_extrude(shape_pts,
radius = 40,
levels = 5,
level_dist = 10,
vt_dir = "SPI_UP"
);
```

```
use <helix_extrude.scad>;
r1 = 40;
r2 = 20;
levels = 5;
level_dist = 10;
shape_pts = [
[10, -2],
[10, 2],
[9, 2],
[9, 0],
[1, 0],
[1, 2],
[0, 2],
[0, -2],
];
helix_extrude(shape_pts,
radius = [r1, r2],
levels = levels,
level_dist = level_dist,
vt_dir = "SPI_UP"
);
%cylinder(h = levels * level_dist, r1 = r1, r2 = r2);
```