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52 lines
1.3 KiB
Markdown
52 lines
1.3 KiB
Markdown
# contours
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Computes contour polygons by applying [marching squares](https://en.wikipedia.org/wiki/Marching_squares) to a rectangular list of numeric values.
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**Since:** 2.3
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## Parameters
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- `points` : 2 value array `[x, y]`, rectangle with dimensions `x` and `y`.
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- `threshold` : When applying a threshold value, the function returns isolines. When applying upper and lower threshold values, it returns isobands.
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## Examples
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use <hull_polyline2d.scad>;
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use <function_grapher.scad>;
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use <contours.scad>;
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min_value = 1;
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max_value = 360;
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resolution = 10;
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function f(x, y) = sin(x) * cos(y) * 30;
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points = [
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for(y = [min_value:resolution:max_value])
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[
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for(x = [min_value:resolution:max_value])
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[x, y, f(x, y)]
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]
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];
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function_grapher(points, 1);
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translate([max_value, 0, 0])
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for(z = [-30:5:30]) {
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translate([0, 0, z])
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linear_extrude(1)
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for(isoline = contours(points, z)) {
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hull_polyline2d(isoline, width = 1);
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}
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}
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translate([0, max_value])
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for(z = [-30:5:30]) {
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linear_extrude(35 + z)
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for(isoband = contours(points, [z, z + 5])) {
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polygon([for(p = isoband) [p[0], p[1]]]);
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}
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}
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