Hi, thanks for the code, but i dont think it makes a good ellipse. I used hull() around the for-loop to illustrate that. See the picture. <http://forum.openscad.org/file/n13330/ellipse2.png> -- View this message in context: http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13330.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Hello guys, @wolf: Sorry i overread in your post that only the inner boundary is an ellipse. You are of course right about that! I made some advancements in creating an elliptic brim with sweep() in scad-utils. However, i dont get why my extruded shape twists around its path with my ellipse equation: <http://forum.openscad.org/file/n13333/twisted_shape.png> Here is my code: use <list-comprehension-demos/sweep.scad> use <scad-utils/transformations.scad> use <scad-utils/shapes.scad> A=450; //long half-axis of ellipse B=300; //short half-axis of ellipse /* function f(t) = [ (t / 1.5 + 0.5) * 100 * cos(6 * 360 * t), (t / 1.5 + 0.5) * 100 * sin(6 * 360 * t), 200 * (1 - t) ]; */ function e(i) = [ 450 * cos(6 * 360 * i), 300 * sin(6 * 360 * i), 0 ]; function shape() = [ [-10, -1], [-10, 6], [ -7, 6], [ -7, 1], [ 7, 1], [ 7, 6], [ 10, 6], [ 10, -1]]; function myshape() = square(10); step = 0.0005; /* path = [for (t=[0:step:1-step]) f(t)]; path_transforms = construct_transform_path(path); sweep(shape(), path_transforms); */ path = [for (i=[0:step:1-step]) e(i)]; path_transforms = construct_transform_path(path); sweep(myshape(), path_transforms); -- View this message in context: http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13333.html Sent from the OpenSCAD mailing list archive at Nabble.com.

On 07/28/2015 03:22 PM, PYM wrote: > I made some advancements in creating an elliptic brim with sweep() in > scad-utils. > > However, i dont get why my extruded shape twists around its path with my > ellipse equation: > <http://forum.openscad.org/file/n13333/twisted_shape.png> > I don't have the math background to explain why it happens, but there's an easy workaround. Just sweep in the X-Z plane by changing e() to function e(i) = [ 450 * cos(6 * 360 * i), 0, 300 * sin(6 * 360 * i) ]; and rotate the result back to X-Y. ciao, Torsten.

No, this does not work: function aa_n(x1,x2,aa)=atan2(x1,x2*tan(aa)); x1 and x2 are constant, they are the two axis of the ellipse a and b ​ 2015-07-28 20:04 GMT+02:00 Torsten Paul <Torsten.Paul@gmx.de>: > On 07/28/2015 03:22 PM, PYM wrote: > >> I made some advancements in creating an elliptic brim with sweep() in >> scad-utils. >> >> However, i dont get why my extruded shape twists around its path with my >> ellipse equation: >> <http://forum.openscad.org/file/n13333/twisted_shape.png> >> >> I don't have the math background to explain why it happens, but there's > an easy workaround. Just sweep in the X-Z plane by changing e() to > > function e(i) = [ > 450 * cos(6 * 360 * i), > 0, > 300 * sin(6 * 360 * i) > ]; > > and rotate the result back to X-Y. > > ciao, > Torsten. > > > > _______________________________________________ > 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 figured it out. This works: // angle of the normal (aa_n) along the ellipse as function of the polar angle (aa) function aa_n(x1,x2,aa)=(aa>270)?atan(x1*tan(aa)/x2):(aa>90)?90+90+atan(x1*tan(aa)/x2):atan(x1*tan(aa)/x2); Now everything looks fine: And the profile is undistorted along every cut through any normal along the ellipse: ​ ​ 2015-07-28 20:23 GMT+02:00 Peter Falke <stempeldergeschichte@googlemail.com> : > No, this does not work: > > function aa_n(x1,x2,aa)=atan2(x1,x2*tan(aa)); > > x1 and x2 are constant, they are the two axis of the ellipse a and b > > > ​ > > 2015-07-28 20:04 GMT+02:00 Torsten Paul <Torsten.Paul@gmx.de>: > >> On 07/28/2015 03:22 PM, PYM wrote: >> >>> I made some advancements in creating an elliptic brim with sweep() in >>> scad-utils. >>> >>> However, i dont get why my extruded shape twists around its path with my >>> ellipse equation: >>> <http://forum.openscad.org/file/n13333/twisted_shape.png> >>> >>> I don't have the math background to explain why it happens, but there's >> an easy workaround. Just sweep in the X-Z plane by changing e() to >> >> function e(i) = [ >> 450 * cos(6 * 360 * i), >> 0, >> 300 * sin(6 * 360 * i) >> ]; >> >> and rotate the result back to X-Y. >> >> ciao, >> Torsten. >> >> >> >> _______________________________________________ >> 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!

The whole point of atan2 is that it covers the full range -180 to 180 because it knows the sign of both the numerator and denominator. atan is only -90 to 90. I think the reason it didn't work is you seem to have changed from x1/x2*tan(aa) to x1*tan(aa)/x2 so it should probably be atan2(x1*tan(aa),x2) in that case. On 28 July 2015 at 19:42, Peter Falke <stempeldergeschichte@googlemail.com> wrote: > OK, I figured it out. This works: > > // angle of the normal (aa_n) along the ellipse as function of the polar > angle (aa) > > function > aa_n(x1,x2,aa)=(aa>270)?atan(x1*tan(aa)/x2):(aa>90)?90+90+atan(x1*tan(aa)/x2):atan(x1*tan(aa)/x2); > > > Now everything looks fine: > > And the profile is undistorted along every cut through any normal along > the ellipse: > > ​ > ​ > > > 2015-07-28 20:23 GMT+02:00 Peter Falke < > stempeldergeschichte@googlemail.com>: > >> No, this does not work: >> >> function aa_n(x1,x2,aa)=atan2(x1,x2*tan(aa)); >> >> x1 and x2 are constant, they are the two axis of the ellipse a and b >> >> >> ​ >> >> 2015-07-28 20:04 GMT+02:00 Torsten Paul <Torsten.Paul@gmx.de>: >> >>> On 07/28/2015 03:22 PM, PYM wrote: >>> >>>> I made some advancements in creating an elliptic brim with sweep() in >>>> scad-utils. >>>> >>>> However, i dont get why my extruded shape twists around its path with my >>>> ellipse equation: >>>> <http://forum.openscad.org/file/n13333/twisted_shape.png> >>>> >>>> I don't have the math background to explain why it happens, but there's >>> an easy workaround. Just sweep in the X-Z plane by changing e() to >>> >>> function e(i) = [ >>> 450 * cos(6 * 360 * i), >>> 0, >>> 300 * sin(6 * 360 * i) >>> ]; >>> >>> and rotate the result back to X-Y. >>> >>> ciao, >>> Torsten. >>> >>> >>> >>> _______________________________________________ >>> 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 > >

x1 and x2 are constant here: only tan(aa) changes, so no look with atan2() 2015-07-28 21:37 GMT+02:00 nop head <nop.head@gmail.com>: > The whole point of atan2 is that it covers the full range -180 to 180 > because it knows the sign of both the numerator and denominator. atan is > only -90 to 90. I think the reason it didn't work is you seem to have > changed from x1/x2*tan(aa) to x1*tan(aa)/x2 so it should probably be > atan2(x1*tan(aa),x2) in that case. > > On 28 July 2015 at 19:42, Peter Falke <stempeldergeschichte@googlemail.com > > wrote: > >> OK, I figured it out. This works: >> >> // angle of the normal (aa_n) along the ellipse as function of the polar >> angle (aa) >> >> function >> aa_n(x1,x2,aa)=(aa>270)?atan(x1*tan(aa)/x2):(aa>90)?90+90+atan(x1*tan(aa)/x2):atan(x1*tan(aa)/x2); >> >> >> Now everything looks fine: >> >> And the profile is undistorted along every cut through any normal along >> the ellipse: >> >> ​ >> ​ >> >> >> 2015-07-28 20:23 GMT+02:00 Peter Falke < >> stempeldergeschichte@googlemail.com>: >> >>> No, this does not work: >>> >>> function aa_n(x1,x2,aa)=atan2(x1,x2*tan(aa)); >>> >>> x1 and x2 are constant, they are the two axis of the ellipse a and b >>> >>> >>> ​ >>> >>> 2015-07-28 20:04 GMT+02:00 Torsten Paul <Torsten.Paul@gmx.de>: >>> >>>> On 07/28/2015 03:22 PM, PYM wrote: >>>> >>>>> I made some advancements in creating an elliptic brim with sweep() in >>>>> scad-utils. >>>>> >>>>> However, i dont get why my extruded shape twists around its path with >>>>> my >>>>> ellipse equation: >>>>> <http://forum.openscad.org/file/n13333/twisted_shape.png> >>>>> >>>>> I don't have the math background to explain why it happens, but >>>> there's >>>> an easy workaround. Just sweep in the X-Z plane by changing e() to >>>> >>>> function e(i) = [ >>>> 450 * cos(6 * 360 * i), >>>> 0, >>>> 300 * sin(6 * 360 * i) >>>> ]; >>>> >>>> and rotate the result back to X-Y. >>>> >>>> ciao, >>>> Torsten. >>>> >>>> >>>> >>>> _______________________________________________ >>>> 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 >> >> > > _______________________________________________ > 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!

Ah I see. Possibly you can split tan(aa) into sin(aa)/cos(aa) and then use atan2(x1 * sin(aa), x2 * cos(aa)) On 28 July 2015 at 21:04, Peter Falke <stempeldergeschichte@googlemail.com> wrote: > x1 and x2 are constant here: only tan(aa) changes, so no look with atan2() > > 2015-07-28 21:37 GMT+02:00 nop head <nop.head@gmail.com>: > >> The whole point of atan2 is that it covers the full range -180 to 180 >> because it knows the sign of both the numerator and denominator. atan is >> only -90 to 90. I think the reason it didn't work is you seem to have >> changed from x1/x2*tan(aa) to x1*tan(aa)/x2 so it should probably be >> atan2(x1*tan(aa),x2) in that case. >> >> On 28 July 2015 at 19:42, Peter Falke < >> stempeldergeschichte@googlemail.com> wrote: >> >>> OK, I figured it out. This works: >>> >>> // angle of the normal (aa_n) along the ellipse as function of the polar >>> angle (aa) >>> >>> function >>> aa_n(x1,x2,aa)=(aa>270)?atan(x1*tan(aa)/x2):(aa>90)?90+90+atan(x1*tan(aa)/x2):atan(x1*tan(aa)/x2); >>> >>> >>> Now everything looks fine: >>> >>> And the profile is undistorted along every cut through any normal along >>> the ellipse: >>> >>> ​ >>> ​ >>> >>> >>> 2015-07-28 20:23 GMT+02:00 Peter Falke < >>> stempeldergeschichte@googlemail.com>: >>> >>>> No, this does not work: >>>> >>>> function aa_n(x1,x2,aa)=atan2(x1,x2*tan(aa)); >>>> >>>> x1 and x2 are constant, they are the two axis of the ellipse a and b >>>> >>>> >>>> ​ >>>> >>>> 2015-07-28 20:04 GMT+02:00 Torsten Paul <Torsten.Paul@gmx.de>: >>>> >>>>> On 07/28/2015 03:22 PM, PYM wrote: >>>>> >>>>>> I made some advancements in creating an elliptic brim with sweep() in >>>>>> scad-utils. >>>>>> >>>>>> However, i dont get why my extruded shape twists around its path with >>>>>> my >>>>>> ellipse equation: >>>>>> <http://forum.openscad.org/file/n13333/twisted_shape.png> >>>>>> >>>>>> I don't have the math background to explain why it happens, but >>>>> there's >>>>> an easy workaround. Just sweep in the X-Z plane by changing e() to >>>>> >>>>> function e(i) = [ >>>>> 450 * cos(6 * 360 * i), >>>>> 0, >>>>> 300 * sin(6 * 360 * i) >>>>> ]; >>>>> >>>>> and rotate the result back to X-Y. >>>>> >>>>> ciao, >>>>> Torsten. >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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 >>> >>> >> >> _______________________________________________ >> 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! > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >

Yes, this works fine. And its much shorter than my piecewise definition: function aa_n(x1,x2,aa)=(aa>270)?atan(x1*tan(aa)/x2):(aa>90)?90+90+atan(x1*tan(aa)/x2):atan(x1*tan(aa)/x2); Thanks

Hi tp3, i did exactly that shortly after my previousand it worked. i Dont understand why though :) -- View this message in context: http://forum.openscad.org/Rotary-extrude-with-constant-wall-thickness-plz-help-tp13287p13364.html Sent from the OpenSCAD mailing list archive at Nabble.com.