dotSCAD VS planar_graph_playground

If you're looking for examples of high quality openscad code, dotSCAD is pretty cool. nophead (old school reprap person and one of the openscad developers) has a parts library that I think is high quality.

Justin Lin passed away due to illness in 2022 at the age of 48.[0]

On December 22, 2022 OpenSCAD posted:

> Today's advent calendar door is a sad one. We'd like to commemorate Justin Lin, who passed away a while ago. In the OpenSCAD community he is best known for his #dotSCAD library. His designs always brought joy and amazement. Thank you, we will miss you.[1,2]

On October 11, 2022 dotSCAD v3.3 released — it was the last commit by JustinSDK on GitHub.[3]

[0] https://www.ithome.com.tw/caterpillar

[1] https://twitter.com/openscad/status/1605758512746881025

[2] https://fosstodon.org/@OpenSCAD/109555037335637650

[3] https://github.com/JustinSDK/dotSCAD/releases/tag/v3.3

https://github.com/JustinSDK/dotSCAD - as far as I can tell this is widely used

I synced your repo: https://github.com/JustinSDK/dotSCAD

// require https://github.com/JustinSDK/dotSCAD use use use n = 5; radius = 10; thickness = 1; geom = geom_icosahedron(radius); points = geom[0]; faces = geom[1]; for(f = faces) { triangle = [for(i = f) points[i]]; // subdivide the triangle triangles = tri_subdivide(triangle, n); points1 = [ for(t = triangles, p = t) let(unit_vector = p / norm(p)) unit_vector * radius ]; points2 = [ for(t = triangles, p = t) let(unit_vector = p / norm(p)) unit_vector * (radius - thickness) ]; ff = [for(i = [0:3:len(points1) - 3]) [i, i + 1, i + 2]]; color(rands(0, 1, 3)) sf_solidifyT(points1, points2, ff); }

If you are into OpenSCAD, grab this chap's work - https://github.com/JustinSDK/dotSCAD/tree/master/src and use his modules, they are rather good.

// use // a shape function from https://github.com/JustinSDK/dotSCAD // sq_outer = shape_square(size = 50, corner_r = 5); sq_outer = [[20, -25], [21.9471, -24.6053], [23.5868, -23.4835], [24.6602, -21.8118], [25, -20], [25, 20], [24.6053, 21.9471], [23.4835, 23.5868], [21.8118, 24.6602], [20, 25], [-20, 25], [-21.8118, 24.6602], [-23.4835, 23.5868], [-24.6053, 21.9471], [-25, 20], [-25, -20], [-24.6602, -21.8118], [-23.5868, -23.4835], [-21.9471, -24.6053], [-20, -25]]; // sq_inner = shape_square(size = 30, corner_r = 3); sq_inner = [[12, -15], [13.8551, -14.3577], [14.9158, -12.7057], [15, -12], [15, 12], [14.3577, 13.8551], [12.7057, 14.9158], [12, 15], [-12, 15], [-12.7057, 14.9158], [-14.3577, 13.8551], [-15, 12], [-15, -12], [-14.9158, -12.7057], [-13.8551, -14.3577], [-12, -15]]; polygon( points = concat(sq_outer, sq_inner), paths = [ [each [0:len(sq_outer) - 1]], [each [len(sq_outer):len(sq_outer)+ len(sq_inner) - 1]] ] );

path_extrude from https://github.com/JustinSDK/dotSCAD library. This kinda works.

I am still learning, and as others wrote I tried to do stuff I wanted and step by step learned how to do so. The comvined modules I created for graph embedding on sphere can be found here (with comment links to formulas for spherical geometry): https://github.com/Hermann-SW/planar_graph_playground/blob/main/scad.js Here you can see for what the "vertex()", "edge2()" and "sp_tria()" modules are used: https://stamm-wilbrandt.de/en/forum/C60.circle_separator.anim.gif

Nice code. But what you want normally is to color the faces of a planar graph with as few colors as possible. The famous four color theorem states that the vertices of a planar graph can always be colored with 4 colors only, with vertices on different sides of each edge being different for all edges. Since dual graph of a planar graph is a planar graph as well (vertices become faces, faces become vertices, edges are kept) the faces of a planar graph can be 4 colored with no neighboring faces having same color. I know of no algorithm to 4-color a planar graph. There is a linear time algorithmto 5-color a plannar graph. I implemented a simple 6-coloring algorithm for planar graphs: https://github.com/Hermann-SW/planar_graph_playground/blob/main/node.convex_face_straight_line_drawing.6coloring.js