On Sun, 28 Dec 2008, Christophe Geuzaine wrote: > Robert Funnell wrote: >> I am trying to create a geometry corresponding to a cylinder which has a >> bend. As shown in the Gmsh code appended below, I am using an extrusion >> with translation, a 2nd extrusion with translation + rotation, and a 3rd >> extrusion with just translation. >> >> The 2nd extrusion begins from the end of the 1st extrusion, as intended. >> However, the final circular surface of the 2nd extrusion isn't located at >> the end of the extrusion, but rather is offset in the y and z directions, >> so the 3rd extrusion doesn't start in the right place. (The effect can be >> seen in the screenshot at >> http://audilab.bmed.mcgill.ca/~funnell/gmsh_bad_extrude.png .) >> >> If I do either translation or rotation alone in the 2nd extrusion, I get >> the results that I expect. >> >> Could someone please explain what I'm doing wrong here? >> > > Your rotation looks weird. Here's an example: > ... > extr2[] = Extrude { {1,0,0}, // direction of rotation axis > {0,2,20}, // a point on the rotation axis > -Pi/2 } { // the rotation angle > Surface{extr1[0]}; > }; > ...
Ah, how embarrassing. I was somehow thinking that I needed to combine an extrusion with the rotation in order to get the desired radius of curvature. And if one combines an extrusion with a rotation in a nonsensical way then one gets a nonsensical result :-) Thank you. - Robert _______________________________________________ gmsh mailing list [email protected] http://www.geuz.org/mailman/listinfo/gmsh
