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Support for twisted cables.

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Sweep now distbutes twists in proportion to segments lengths.
Added  spiral_paths(), segmented_path() and rounded_path_vertices() functions.
Added show_path(path) module.
This commit is contained in:
Chris Palmer
2022-02-08 19:08:10 +00:00
parent 136584d086
commit 1f55097bdd
31 changed files with 70 additions and 7 deletions
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61
utils/sweep.scad
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@@ -29,6 +29,8 @@
//! `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.
//!
//! `spiral_paths()` makes a list of new paths that spiral around a given path. It can be used to make twisted wires that follow a rounded_path, for example.
//
include <../utils/core/core.scad>
@@ -107,18 +109,19 @@ function helical_twist_per_segment(r, pitch, sides) = //! Calculate the twist ar
) step_angle * sin(slope); // angle tangent should rotate around z projected onto axis rotate_from_to() uses
//
// Generate all the surface points of the swept volume.
// Generate all the transforms for the profile of the swept volume.
//
function skin_points(profile, path, loop, twist = 0) =
function sweep_transforms(path, loop = false, twist = 0) =
let(len = len(path),
last = len - 1,
profile4 = [for(p = profile) [p.x, p.y, p.z, 1]],
tangents = [tangent(path, loop ? last : 0, 0, 1),
for(i = [1 : last - 1]) tangent(path, i - 1, i, i + 1),
tangent(path, last - 1, last, loop ? 0 : last)],
lengths = [for(i = 0, t = 0; i < len; t = t + norm(path[min(i + 1, last)] - path[i]), i = i + 1) t],
length = lengths[last],
rotations = [for(i = 0, rot = fs_frame(tangents);
i < len;
i = i + 1,
@@ -128,8 +131,20 @@ function skin_points(profile, path, loop, twist = 0) =
rotation = missmatch + twist
)
[for(i = [0 : last])
let(za = rotation * i / last)
each profile4 * orientate(path[i], rotations[i] * rot3_z(za))
let(za = rotation * lengths[i] / length)
orientate(path[i], rotations[i] * rot3_z(za))
];
//
// Generate all the surface points of the swept volume.
//
function skin_points(profile, path, loop, twist = 0) =
let(profile4 = [for(p = profile) [p.x, p.y, p.z, 1]],
transforms = sweep_transforms(path, loop, twist)
)
[for(t = transforms)
each profile4 * t
];
function cap(facets, segment = 0, end) = //! Create the mesh for an end cap
@@ -211,3 +226,37 @@ function rounded_path(path) = //! Convert a rounded_path, consisting of a start
cos(t) * x_axis + sin(t) * y_axis + centre, // Circular arc in the tiled xy plane.
path[len - 1], // Last point has no radius
];
function segmented_path(path, min_segment) = [ //! Add points to a path to enforce a minimum segment length
for(i = [0 : len(path) - 2])
let(delta =
assert(path[i] != path[i + 1], str("Coincident points at path[", i, "] = ", path[i]))
path[i+1] - path[i],
segs = ceil(norm(delta) / min_segment)
)
for(j = [0 : segs - 1])
path[i] + delta * j / segs, // Linear interpolation
path[len(path) - 1]
];
function spiral_paths(path, n, r, twists, start_angle) = let( //! Create a new paths which sprial around the given path. Use for making twisted cables
segment = path_length(path) / twists / r2sides(2 * r),
transforms = sweep_transforms(segmented_path(path, segment), twist = 360 * twists),
initial = [r, 0, 0, 1] * rotate(start_angle)
) [for(i = [0 : n - 1]) let(initial = [r, 0, 0, 1] * rotate(start_angle + i * 360 / n)) [for(t = transforms) initial * t]];
function rounded_path_vertices(path) = [path[0], for(i = [1 : 2 : len(path) - 1]) path[i]]; //! Show the unrounded version of a rounded_path for debug
module show_path(path) //! Show a path using a chain of hulls for debugging, duplicate points are highlighted.
for(i = [0 : len(path) - 2]) {
hull($fn = 16) {
translate(path[i])
sphere(0.1);
translate(path[i + 1])
sphere(0.1);
}
if(path[i] == path[i + 1])
translate(path[i])
color("red") sphere(1);
}