​Is this what you want? module shape(){ polygon( points=[[0,0],[2,1],[1,2],[1,3],[3,4],[0,5]] ); } $fn = 32; difference(){ offset(r=.5)shape(); shape(); } %color("red")shape(); 2015-07-27 11:46 GMT+02:00 PYM <pm@pixelyourmind.de>: > Hello, > > actually that works good for a cylinder object, but it doesnt work for a > complex shape like > > polygon( points=[[0,0],[2,1],[1,2],[1,3],[3,4],[0,5]] ); > > The cross section of my brim is a complex profile. How can i do that? > > Please help! > > > > > > -- > View this message in context: > http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13319.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 > -- stempeldergeschichte@googlemail.com <karsten@rohrbach.de> P.S. Falls meine E-Mail kürzer ausfällt als Dir angenehm ist: Ich probiere gerade aus kurze Antworten statt gar keine Antworten zu schreiben. Wenn Du gerne mehr lesen möchtest, dann lass es mich bitte wissen. P.S. In case my e-mail is shorter than you enjoy: I am currently trying short replies instead of no replies at all. Please let me know, if you like to read more. Enjoy!

Hello Peter, no not really, see the link <http://forum.openscad.org/Please-help-with-path-extrusion-td13322.html> for a quick sketch of what i need. Maybe an admin can actually merge this Thread and the linked one? -- View this message in context: http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13329.html Sent from the OpenSCAD mailing list archive at Nabble.com.

This may not help your case directly, but here's one way to use 2D Minkowski to create an extension in a particular direction for an arbitrary 2D shape: https://github.com/clothbot/ClothBotCreations/blob/master/examples/directional_minkowski.scad You can then use it as a mask for other shapes, features, etc. Enable "Animation" for fun; looks kinda like a projected shadow. Andrew. -- View this message in context: http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13335.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Here is my first take on the brim problem. This is done by chain-hull()ing the profile at angle aa and aa+delta aa, respectively. One problem of chain-hull()ing is that it can only handle convex profiles, therefore the profile of the vessel is subtracted by parts. (The second problem is that it gets slow for higher resolution (here $fn and fn_a)) But there is still a problem with the angle of the profile along the ellipse: the profile points in the direction of the angle aa, but it should point along the normal of the ellipse at angle aa. This can be seen in the third picture. Now this will require some work with trigonometry and a pencil. :( Or does someone know the angle of the normal on an ellipse as function of the angle of the "radius"? The code is in the appendix. >From below: Miss aligned profile: ​ ​ 2015-07-28 16:59 GMT+02:00 clothbot <andrew@plumb.org>: > This may not help your case directly, but here's one way to use 2D > Minkowski > to create an extension in a particular direction for an arbitrary 2D shape: > > > https://github.com/clothbot/ClothBotCreations/blob/master/examples/directional_minkowski.scad > > You can then use it as a mask for other shapes, features, etc. > > Enable "Animation" for fun; looks kinda like a projected shadow. > > Andrew. > > > > > -- > View this message in context: > http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13335.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 > -- stempeldergeschichte@googlemail.com <karsten@rohrbach.de> P.S. Falls meine E-Mail kürzer ausfällt als Dir angenehm ist: Ich probiere gerade aus kurze Antworten statt gar keine Antworten zu schreiben. Wenn Du gerne mehr lesen möchtest, dann lass es mich bitte wissen. P.S. In case my e-mail is shorter than you enjoy: I am currently trying short replies instead of no replies at all. Please let me know, if you like to read more. Enjoy!

Ok, I found the normal angle as a function of polar angle. // angle of the normal (aa_n) along the ellipse as function of the polar angle (aa) function aa_n(x1,x2,aa)=atan(x1/x2*tan(aa)); The problem I now have is that atan(tan(aa)) diverges at aa=90 (and 270) degree. How do I fix that? ​ 2015-07-28 18:23 GMT+02:00 Peter Falke <stempeldergeschichte@googlemail.com> : > Here is my first take on the brim problem. > This is done by chain-hull()ing the profile at angle aa and aa+delta aa, > respectively. > One problem of chain-hull()ing is that it can only handle convex profiles, > therefore the profile of the vessel is subtracted by parts. > (The second problem is that it gets slow for higher resolution (here $fn > and fn_a)) > > But there is still a problem with the angle of the profile along the > ellipse: the profile points in the direction of the angle aa, but it should > point along the normal of the ellipse at angle aa. > This can be seen in the third picture. > Now this will require some work with trigonometry and a pencil. :( > Or does someone know the angle of the normal on an ellipse as function of > the angle of the "radius"? > > The code is in the appendix. > > From below: > > Miss aligned profile: > > > > ​ > ​ > > 2015-07-28 16:59 GMT+02:00 clothbot <andrew@plumb.org>: > >> This may not help your case directly, but here's one way to use 2D >> Minkowski >> to create an extension in a particular direction for an arbitrary 2D >> shape: >> >> >> https://github.com/clothbot/ClothBotCreations/blob/master/examples/directional_minkowski.scad >> >> You can then use it as a mask for other shapes, features, etc. >> >> Enable "Animation" for fun; looks kinda like a projected shadow. >> >> Andrew. >> >> >> >> >> -- >> View this message in context: >> http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13335.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 >> > > > > -- > stempeldergeschichte@googlemail.com <karsten@rohrbach.de> > > P.S. Falls meine E-Mail kürzer ausfällt als Dir angenehm ist: > Ich probiere gerade aus kurze Antworten statt gar keine Antworten zu > schreiben. > Wenn Du gerne mehr lesen möchtest, dann lass es mich bitte wissen. > > P.S. In case my e-mail is shorter than you enjoy: > I am currently trying short replies instead of no replies at all. > Please let me know, if you like to read more. > > Enjoy! > -- stempeldergeschichte@googlemail.com <karsten@rohrbach.de> P.S. Falls meine E-Mail kürzer ausfällt als Dir angenehm ist: Ich probiere gerade aus kurze Antworten statt gar keine Antworten zu schreiben. Wenn Du gerne mehr lesen möchtest, dann lass es mich bitte wissen. P.S. In case my e-mail is shorter than you enjoy: I am currently trying short replies instead of no replies at all. Please let me know, if you like to read more. Enjoy!

Use atan2((x1,x2*tan(aa)) On 28 July 2015 at 18:50, Peter Falke <stempeldergeschichte@googlemail.com> wrote: > Ok, I found the normal angle as a function of polar angle. > > // angle of the normal (aa_n) along the ellipse as function of the polar > angle (aa) > function aa_n(x1,x2,aa)=atan(x1/x2*tan(aa)); > > The problem I now have is that atan(tan(aa)) diverges at aa=90 (and 270) > degree. > How do I fix that? > > > ​ > > 2015-07-28 18:23 GMT+02:00 Peter Falke < > stempeldergeschichte@googlemail.com>: > >> Here is my first take on the brim problem. >> This is done by chain-hull()ing the profile at angle aa and aa+delta aa, >> respectively. >> One problem of chain-hull()ing is that it can only handle convex >> profiles, therefore the profile of the vessel is subtracted by parts. >> (The second problem is that it gets slow for higher resolution (here $fn >> and fn_a)) >> >> But there is still a problem with the angle of the profile along the >> ellipse: the profile points in the direction of the angle aa, but it should >> point along the normal of the ellipse at angle aa. >> This can be seen in the third picture. >> Now this will require some work with trigonometry and a pencil. :( >> Or does someone know the angle of the normal on an ellipse as function of >> the angle of the "radius"? >> >> The code is in the appendix. >> >> From below: >> >> Miss aligned profile: >> >> >> >> ​ >> ​ >> >> 2015-07-28 16:59 GMT+02:00 clothbot <andrew@plumb.org>: >> >>> This may not help your case directly, but here's one way to use 2D >>> Minkowski >>> to create an extension in a particular direction for an arbitrary 2D >>> shape: >>> >>> >>> https://github.com/clothbot/ClothBotCreations/blob/master/examples/directional_minkowski.scad >>> >>> You can then use it as a mask for other shapes, features, etc. >>> >>> Enable "Animation" for fun; looks kinda like a projected shadow. >>> >>> Andrew. >>> >>> >>> >>> >>> -- >>> View this message in context: >>> http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13335.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 >>> >> >> >> >> -- >> stempeldergeschichte@googlemail.com <karsten@rohrbach.de> >> >> P.S. Falls meine E-Mail kürzer ausfällt als Dir angenehm ist: >> Ich probiere gerade aus kurze Antworten statt gar keine Antworten zu >> schreiben. >> Wenn Du gerne mehr lesen möchtest, dann lass es mich bitte wissen. >> >> P.S. In case my e-mail is shorter than you enjoy: >> I am currently trying short replies instead of no replies at all. >> Please let me know, if you like to read more. >> >> Enjoy! >> > > > > -- > stempeldergeschichte@googlemail.com <karsten@rohrbach.de> > > P.S. Falls meine E-Mail kürzer ausfällt als Dir angenehm ist: > Ich probiere gerade aus kurze Antworten statt gar keine Antworten zu > schreiben. > Wenn Du gerne mehr lesen möchtest, dann lass es mich bitte wissen. > > P.S. In case my e-mail is shorter than you enjoy: > I am currently trying short replies instead of no replies at all. > Please let me know, if you like to read more. > > Enjoy! > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >