GNAL/spiral/spiral_4.scad

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D=300; // start diameter
N=1; // number of spirals
FN=100;
$fn=FN;
include <../libraries/path_extrude.scad>;
/**
* Distinction from spiral_3: use of for loop and union to join rotations. Somehow
* got it into my head that this was faster? It does adjust the facet size to the
* diameter.
**/
module spiral (count = 40, start_d = 48, spacing = 2.075) {
facet_size = 30;
bottom = 1.2;
top = .4;
top_offset = (bottom - top);
h = 2.2;
od = start_d + (spacing * 2 * count);
echo("SPIRAL LENGTH", PI * count * (od + start_d + 1) / 2);
echo("OUTER D", od);
facetProfile = [[0, 0], [top_offset, -h], [bottom, -h], [bottom, 0]];
union () {
for (s = [0 : count - 1]) {
d = start_d + (s * spacing * 2);
c = PI * pow(d / 2, 2);
$fn = ceil( c / facet_size );
angle_i = 360 / $fn;
increment = spacing / $fn;
spiralPath = [ for(t = [0 : $fn + 1]) [((d / 2) + (t * increment)) * cos(t * angle_i), ((d / 2) + (t * increment)) * sin(t * angle_i), 0] ];
path_extrude(exShape=facetProfile, exPath=spiralPath);
}
}
}
spiral(N, D);