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dotSCAD/docs/lib2x-path_scaling_sections.md
2020-01-28 17:51:20 +08:00

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# path_scaling_sections
Given an edge path with the first point at the outline of a shape. This function uses the path to calculate scaling factors and returns all scaled sections in the reversed order of the edge path. Combined with the `polysections` module, you can create an extrusion with the path as an edge.
In order to control scaling factors easily, I suggest using `[x, 0, 0]` as the first point and keeping y = 0 while building the edge path.
You can use any point as the first point of the edge path. Just remember that your edge path radiates from the origin.
**Since:** 1.2.
## Parameters
- `shape_pts` : A list of points represent a shape.
- `edge_path` : A list of points represent the edge path.
## Examples
use <hull_polyline3d.scad>;
use <shape_taiwan.scad>;
use <path_scaling_sections.scad>;
use <polysections.scad>;
taiwan = shape_taiwan(100);
fst_pt = [13, 0, 0];
edge_path = [
fst_pt,
fst_pt + [0, 0, 10],
fst_pt + [10, 0, 20],
fst_pt + [8, 0, 30],
fst_pt + [12, 0, 40],
fst_pt + [0, 0, 50],
fst_pt + [0, 0, 60]
];
#hull_polyline3d(edge_path);
polysections(path_scaling_sections(taiwan, edge_path));
![path_scaling_sections](images/lib-path_scaling_sections-1.JPG)
use <hull_polyline3d.scad>;
use <shape_taiwan.scad>;
use <path_scaling_sections.scad>;
use <polysections.scad>;
use <bezier_curve.scad>;
taiwan = shape_taiwan(100);
fst_pt = [13, 0, 0];
edge_path = bezier_curve(0.05, [
fst_pt,
fst_pt + [0, 0, 10],
fst_pt + [10, 0, 20],
fst_pt + [8, 0, 30],
fst_pt + [12, 0, 40],
fst_pt + [0, 0, 50],
fst_pt + [0, 0, 60]
]);
#hull_polyline3d(edge_path);
polysections(path_scaling_sections(taiwan, edge_path));
![path_scaling_sections](images/lib-path_scaling_sections-2.JPG)
use <shape_taiwan.scad>;
use <path_scaling_sections.scad>;
use <polysections.scad>;
use <bezier_curve.scad>;
use <rotate_p.scad>;
taiwan = shape_taiwan(100);
fst_pt = [13, 0, 0];
edge_path = bezier_curve(0.05, [
fst_pt,
fst_pt + [0, 0, 10],
fst_pt + [10, 0, 20],
fst_pt + [8, 0, 30],
fst_pt + [12, 0, 40],
fst_pt + [0, 0, 50],
fst_pt + [0, 0, 60]
]);
leng = len(edge_path);
twist = -90;
twist_step = twist / leng;
sections = path_scaling_sections(taiwan, edge_path);
rotated_sections = [
for(i = [0:leng - 1])
[
for(p = sections[i])
rotate_p(p, twist_step * i)
]
];
polysections(rotated_sections);
![path_scaling_sections](images/lib-path_scaling_sections-3.JPG)
use <hull_polyline3d.scad>;
use <shape_taiwan.scad>;
use <path_scaling_sections.scad>;
use <polysections.scad>;
use <rotate_p.scad>;
taiwan = shape_taiwan(100);
/*
You can use any point as the first point of the edge path.
Just remember that your edge path radiates from the origin.
*/
fst_pt = [taiwan[0][0], taiwan[0][1], 0];//[13, 0, 0];
a = atan2(fst_pt[1], fst_pt[0]);
edge_path = [
fst_pt,
fst_pt + rotate_p([0, 0, 10], a),
fst_pt + rotate_p([10, 0, 20], a),
fst_pt + rotate_p([8, 0, 30], a),
fst_pt + rotate_p([10, 0, 40], a),
fst_pt + rotate_p([0, 0, 50], a),
fst_pt + rotate_p([0, 0, 60], a)
];
#hull_polyline3d(edge_path);
polysections(path_scaling_sections(taiwan, edge_path));
![path_scaling_sections](images/lib-path_scaling_sections-4.JPG)