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146 lines
3.5 KiB
Markdown
146 lines
3.5 KiB
Markdown
# polysections
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Crosscutting a tube-like shape at different points gets several cross-sections. This module can operate reversely. It uses cross-sections to construct a tube-like shape. For example, imagine that you have the following cross-sections:
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This module can use them to construct the following model:
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Looks like extruding along the path? Yes, it can perform the task; however, it's more flexible.
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You can also view it as a better polyline3d module if you want. If you have only the points of a path, using `polyline3d` or `hull_polyline3d` is a simple solution. If you know the cross-sections along a path, you can use `polysections` to do more.
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When using this module, you should use points to represent each cross-section. You need to provide indexes of triangles, too. This module provides two prepared triangles indexes. One is `"RADIAL"`. For example, if you have a cross-section such as:
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When using `"RADIAL"` (default), the module will cut them into triangles from the first point to each remaining point:
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If your cross-sections are hollow, you may use `"HOLLOW"`. For example:
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When using `"HOLLOW"`, the above shape will be cut into triangles such as:
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You can cut triangles by yourself, for example, the indexes of the above triangles is:
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[
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[0, 3, 4],
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[0, 4, 1],
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[1, 4, 5],
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[1, 5, 2],
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[2, 5, 3],
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[2, 3, 0]
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]
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Triangles may be defined in any order.
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## Parameters
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- `sections` : A list of cross-sections. Each cross-section is represented by a list of points. See the example below.
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- `triangles` : `"RADIAL"` (default), `"HOLLOW"` or user-defined indexes. See example below.
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## Examples
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include <rotate_p.scad>;
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include <polysections.scad>;
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section1 = [
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[10, 0, 0],
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[15, 10, 0],
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[18, 9, 0],
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[20, 0, 0]
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];
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// spin section1
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sections = [
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for(i = [0:55])
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[
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for(p = section1)
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let(pt = rotate_p(p, [90, 0, -10 * i]))
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[pt[0], pt[1] , pt[2] + i]
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]
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];
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polysections(sections);
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include <rotate_p.scad>;
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include <polysections.scad>;
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section1 = [
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// outer
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[10, 0, 0],
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[15, 10, 0],
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[18, 9, 0],
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[20, 0, 0],
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// inner
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[12, 2, 0],
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[15, 7, 0],
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[17, 7, 0],
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[18, 2, 0]
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];
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// spin section1
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sections = [
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for(i = [0:55])
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[
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for(p = section1)
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let(pt = rotate_p(p, [90, 0, -10 * i]))
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[pt[0], pt[1] , pt[2] + i]
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]
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];
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polysections(sections, "HOLLOW");
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include <rotate_p.scad>;
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include <polysections.scad>;
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section1 = [
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// outer
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[10, 0, 0],
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[15, 10, 0],
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[30, 0, 0],
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// inner
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[12, 1, 0],
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[15, 8, 0],
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[26, 1, 0],
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];
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// spin section1
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sections = [
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for(i = [0:55])
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[
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for(p = section1)
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let(pt = rotate_p(p, [90, 0, -10 * i]))
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[pt[0], pt[1] , pt[2] + i]
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]
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];
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polysections(
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sections = sections,
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triangles = [
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[0, 3, 4],
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[0, 4, 1],
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[1, 4, 5],
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[1, 5, 2],
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[2, 5, 3],
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[2, 3, 0]
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]
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);
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