How about using my *helix_extrude* module? https://github.com/JustinSDK/dotSCAD/blob/master/docs/lib-helix_extrude.md include <helix.scad>; include <rotate_p.scad>; include <cross_sections.scad>; include <polysections.scad>; include <helix_extrude.scad>; r1 = 40; r2 = 20; levels = 5; level_dist = 10; shape_pts = [ [0, -2], [0, 2], [1, 2], [1, 0], [9, 0], [9, 2], [10, 2], [10, -2] ]; helix_extrude(shape_pts, radius = [r1, r2], levels = levels, level_dist = level_dist, vt_dir = "SPI_UP", triangles = [ [0, 1, 2], [0, 2, 3], [0, 3, 4], [0, 4, 7], [4, 5, 6], [4, 6, 7] ] ); %cylinder(h = levels * level_dist, r1 = r1, r2 = r2); <http://forum.openscad.org/file/n21419/lib-helix_extrude-2.jpg> ----- http://openhome.cc -- View this message in context: http://forum.openscad.org/screw-thread-around-a-cone-tp20965p21419.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Interesting approach. It sweeps convex eventually holed 2D shapes. However, as it breaks the sweep in so many small triangular prisms, I would expect an even longer render time. 2017-05-06 9:44 GMT-03:00 caterpillar <caterpillar@openhome.cc>: > How about using my *helix_extrude* module? > > https://github.com/JustinSDK/dotSCAD/blob/master/docs/lib-helix_extrude.md > > include <helix.scad>; > include <rotate_p.scad>; > include <cross_sections.scad>; > include <polysections.scad>; > include <helix_extrude.scad>; > > r1 = 40; > r2 = 20; > levels = 5; > level_dist = 10; > > shape_pts = [ > [0, -2], [0, 2], > [1, 2], [1, 0], > [9, 0], [9, 2], > [10, 2], [10, -2] > ]; > > helix_extrude(shape_pts, > radius = [r1, r2], > levels = levels, > level_dist = level_dist, > vt_dir = "SPI_UP", > triangles = [ > [0, 1, 2], > [0, 2, 3], > [0, 3, 4], > [0, 4, 7], > [4, 5, 6], > [4, 6, 7] > ] > ); > > %cylinder(h = levels * level_dist, r1 = r1, r2 = r2); > > <http://forum.openscad.org/file/n21419/lib-helix_extrude-2.jpg> > > > > > ----- > http://openhome.cc > -- > View this message in context: http://forum.openscad.org/ > screw-thread-around-a-cone-tp20965p21419.html > Sent from the OpenSCAD mailing list archive at Nabble.com. > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

In my computer, it takes about 1 minute to render this example. <http://forum.openscad.org/file/n21421/captured.jpg> ----- http://openhome.cc -- View this message in context: http://forum.openscad.org/screw-thread-around-a-cone-tp20965p21421.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Thanks for Ronaldo's reminder. I finally improved the extrusion performance of solid or hollow shapes. It takes short time even you render the horn below. include <circle_path.scad>; include <rotate_p.scad>; include <golden_spiral.scad>; include <cross_sections.scad>; include <polysections.scad>; include <golden_spiral_extrude.scad>; $fn = 12; shape_pts = concat( circle_path(radius = 3), circle_path(radius = 2) ); golden_spiral_extrude( shape_pts, from = 5, to = 10, point_distance = 1, scale = 10, triangles = "HOLLOW" ); <http://forum.openscad.org/file/n21422/lib-golden_spiral_extrude-2.jpg> I still reserve the triangles parameter for users who want to define a more complex shape. ----- http://openhome.cc -- View this message in context: http://forum.openscad.org/screw-thread-around-a-cone-tp20965p21422.html Sent from the OpenSCAD mailing list archive at Nabble.com.