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Added rounded_path() function to sweep.scad.

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Chris Palmer
2022-02-06 23:44:23 +00:00
parent d341ce499e
commit 225ea9b451
4 changed files with 46 additions and 6 deletions
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32
utils/sweep.scad
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@@ -25,6 +25,10 @@
//!
//! The path can be open or closed. If closed sweep ensures that the start and end have the same rotation to line up.
//! An additional twist around the path can be specified. If the path is closed this should be a multiple of 360.
//!
//! `rounded_path()` can be used to generate a path of lines connected by arcs, useful for wire runs, etc.
//! The vertices specify where the the path would be without any rounding.
//! Each vertex, apart from the first and the last, has an associated radius and the path shortcuts the vertex with an arc specified by the radius.
//
include <../utils/core/core.scad>
@@ -179,3 +183,31 @@ function before(path1, path2) = //! Translate `path1` so its end meets the star
function after(path1, path2) = //! Translate `path2` so its start meets the end of `path1` and then concatenate
let(end1 = len(path1) - 1, end2 = len(path2) - 1, offset = path1[end1] - path2[0])
concat(path1, [for(i = [1 : end2]) path2[i] + offset]);
function rounded_path(path) = //! Convert a rounded_path, consisting of a start coordinate, vertex / radius pairs and then an end coordinate, to a path of points for sweep.
let(len = len(path)) assert(len > 3 && len % 2 == 0) [
path[0], // First point has no radius
for(i = [1 : 2 : len - 3]) let( // Step through the vertices with radii, i.e. not the first or last
prev = max(i - 2, 0), // Index of previous point, might be the first point, which is a special case
p0 = path[prev], // Point before the vertex
p1 = path[i], // Vertex
r = path[i + 1], // Radius of shortcut curve
p2 = path[i + 2], // Point after the vertex
v1 = assert(Len(p0) == 3, str("expected path[", prev, "] to be a vertex coordinate, got ", p0))
assert(Len(p1) == 3, str("expected path[", i, "] to be a vertex coordinate, got ", p1))
assert(Len(p2) == 3, str("expected path[", i + 2, "] to be a vertex coordinate, got ", p2))
assert(is_num(r), str("expected path[", i + 1, "] to be a radius, got ", r))
p0 - p1, // Calculate vectors between vertices
v2 = p2 - p1,
a = angle_between(v1, -v2), // Angle turned through
arc_start = p1 + unit(v1) * r * tan(a / 2), // Calc the start position
z_axis = unit(cross(v1, v2)), // z_axis is perpendicular to both vectors
centre = arc_start + unit(cross(z_axis, v1)) * r, // Arc center is a radius away, and perpendicular to v1 and the z_axis.
x_axis = arc_start - centre, // Make the x_axis along the radius to the start point, includes radius a scale factor
y_axis = cross(x_axis, z_axis), // y_axis perpendicular to the other two
sides = r2sides(ceil(r2sides(r) * a / 360)) // Sides needed to make the arc
)
for(j = [0 : sides], t = a * j / sides) // For each vertex in the arc
cos(t) * x_axis + sin(t) * y_axis + centre, // Circular arc in the tiled xy plane.
path[len - 1], // Last point has no radius
];