60 lines
2.0 KiB
OpenSCAD
60 lines
2.0 KiB
OpenSCAD
D=300; // start diameter
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N=1; // number of spirals
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FN=100;
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$fn=FN;
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include <../libraries/path_extrude.scad>;
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bottom = 1.2;
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top = .3;
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top_offset = (bottom - top);
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h = 2.2;
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facetProfile = [[0, 0], [top_offset, -h], [bottom, -h], [bottom, 0]];
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function X (start_r, spacing, fn, r, i) = (start_r + (r * spacing) + (i * calcIncrement(spacing, fn))) * cos(i * calcAngle(fn));
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function Y (start_r, spacing, fn, r, i) = (start_r + (r * spacing) + (i * calcIncrement(spacing, fn))) * sin(i * calcAngle(fn));
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function circ (d) = PI * d;
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function calcFacetSize (end_d, fn) = circ( end_d ) / fn;
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//function calcSteps(rotations, fn) = fn * rotations;
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function calcAngle (fn) = 360 / fn;
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function calcFn(start_d, start_fn, end_d, spacing, r) = start_fn +
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( ((circ(calcR(start_d, spacing, r) * 2) - circ(start_d) )
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/ (circ(end_d) - circ(start_d))) * ($fn - start_fn));
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function calcR(start_d, spacing, r) = (start_d / 2) + (spacing * r);
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function calcIncrement(spacing, fn) = spacing / fn;
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/**
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* spiral_7 - Combination of spiral_3 and spiral_4 that doesn't sacrifice
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* performance. Hits an overflow when $fn is higher than 245 which creates
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* 8418 vectors at 60 rotations. This is an edge case, only appearing in OpenSCAD
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* 2019.05 (and maybe earlier), but should be explored.
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**/
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module spiral (rotations = 40, start_d = 48, spacing = 2.075, fn) {
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end_d = start_d + (spacing * 2 * rotations);
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end_r = end_d / 2;
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start_r = start_d / 2;
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facetSize = calcFacetSize(end_d, fn);
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start_fn = round(circ(start_d) / facetSize);
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echo(facetSize);
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spiralPath = [ for (r = [0 : rotations - 1]) for (i = [0 : round(calcFn(start_d, start_fn, end_d, spacing, r )) - 1 ])
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[
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X(start_r, spacing, round(calcFn(start_d, start_fn, end_d, spacing, r )), r, i),
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Y(start_r, spacing, round(calcFn(start_d, start_fn, end_d, spacing, r )), r, i),
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0]
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];
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echo(len(spiralPath));
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path_extrude(exShape=facetProfile, exPath=spiralPath);
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}
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spiral(N, D, 2.075, $fn);
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