*Already for weeks I am working on a configurable clarinet mouthpiece design. I make use of the sweep functions make the objects. I make three different stl files to keep the speed acceptable. - The outside - the inside - the beak ; a part that is cut from the outside part too. The combination file looks like this:* module mouthpiece () { difference()// body minus tafel { import("mouthpiece outside v11.stl"); import("mouthpiece inside v11.stl"); import("mouthpiece beak v11.stl"); } } *The problem is that combinations of the outside and the beak gives an error using F6. I already check both objects with meshLab. The are allright. What can be wrong?* *This is the output of the console:* /Saved backup file: C:/Users/Eigenaar/Documents/OpenSCAD/backups/mouthpiece-backup-gqHp8304.scad Compiling design (CSG Tree generation)... Rendering Polygon Mesh using CGAL... ERROR: CGAL error in CGALUtils::applyBinaryOperator difference: CGAL ERROR: assertion violation! Expr: itl != it->second.end() File: /data/OpenSCAD/libraries-mingw32-master/mxe/usr/i686-w64-mingw32.static/include/CGAL/Nef_3/SNC_external_structure.h Line: 1102 Geometries in cache: 8 Geometry cache size in bytes: 13645112 CGAL Polyhedrons in cache: 4 CGAL cache size in bytes: 97234272 Total rendering time: 0 hours, 1 minutes, 33 seconds Top level object is a 3D object: Simple: yes Vertices: 18712 Halfedges: 109364 Edges: 54682 Halffacets: 71950 Facets: 35975 Volumes: 2 Rendering finished./ mouthpiece_beak_v11.stl <http://forum.openscad.org/file/n15909/mouthpiece_beak_v11.stl> mouthpiece_outside_v11.scad <http://forum.openscad.org/file/n15909/mouthpiece_outside_v11.scad> mouthpiece_inside_v11.stl <http://forum.openscad.org/file/n15909/mouthpiece_inside_v11.stl> -- View this message in context: http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Perhaps they intersect, so that although each mesh is manifold, the result isn't. On 27 January 2016 at 11:42, Johan Jonker <johangjonker@zonnet.nl> wrote: > *Already for weeks I am working on a configurable clarinet mouthpiece > design. > I make use of the sweep functions make the objects. > > I make three different stl files to keep the speed acceptable. > - The outside > - the inside > - the beak ; a part that is cut from the outside part too. > > The combination file looks like this:* > module mouthpiece () > { > difference()// body minus tafel > { > import("mouthpiece outside v11.stl"); > import("mouthpiece inside v11.stl"); > import("mouthpiece beak v11.stl"); > } > } > > *The problem is that combinations of the outside and the beak gives an > error > using F6. > I already check both objects with meshLab. The are allright. What can be > wrong?* > > *This is the output of the console:* > /Saved backup file: > > C:/Users/Eigenaar/Documents/OpenSCAD/backups/mouthpiece-backup-gqHp8304.scad > Compiling design (CSG Tree generation)... > Rendering Polygon Mesh using CGAL... > ERROR: CGAL error in CGALUtils::applyBinaryOperator difference: CGAL ERROR: > assertion violation! Expr: itl != it->second.end() File: > > /data/OpenSCAD/libraries-mingw32-master/mxe/usr/i686-w64-mingw32.static/include/CGAL/Nef_3/SNC_external_structure.h > Line: 1102 > Geometries in cache: 8 > Geometry cache size in bytes: 13645112 > CGAL Polyhedrons in cache: 4 > CGAL cache size in bytes: 97234272 > Total rendering time: 0 hours, 1 minutes, 33 seconds > Top level object is a 3D object: > Simple: yes > Vertices: 18712 > Halfedges: 109364 > Edges: 54682 > Halffacets: 71950 > Facets: 35975 > Volumes: 2 > Rendering finished./ > > mouthpiece_beak_v11.stl > <http://forum.openscad.org/file/n15909/mouthpiece_beak_v11.stl> > mouthpiece_outside_v11.scad > <http://forum.openscad.org/file/n15909/mouthpiece_outside_v11.scad> > mouthpiece_inside_v11.stl > <http://forum.openscad.org/file/n15909/mouthpiece_inside_v11.stl> > > > > -- > View this message in context: > http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909.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 >

On second thoughts that shouldn't be a problem. Please can you attach the STL for the outside. On 27 January 2016 at 11:48, nop head <nop.head@gmail.com> wrote: > Perhaps they intersect, so that although each mesh is manifold, the result > isn't. > > On 27 January 2016 at 11:42, Johan Jonker <johangjonker@zonnet.nl> wrote: > >> *Already for weeks I am working on a configurable clarinet mouthpiece >> design. >> I make use of the sweep functions make the objects. >> >> I make three different stl files to keep the speed acceptable. >> - The outside >> - the inside >> - the beak ; a part that is cut from the outside part too. >> >> The combination file looks like this:* >> module mouthpiece () >> { >> difference()// body minus tafel >> { >> import("mouthpiece outside v11.stl"); >> import("mouthpiece inside v11.stl"); >> import("mouthpiece beak v11.stl"); >> } >> } >> >> *The problem is that combinations of the outside and the beak gives an >> error >> using F6. >> I already check both objects with meshLab. The are allright. What can be >> wrong?* >> >> *This is the output of the console:* >> /Saved backup file: >> >> C:/Users/Eigenaar/Documents/OpenSCAD/backups/mouthpiece-backup-gqHp8304.scad >> Compiling design (CSG Tree generation)... >> Rendering Polygon Mesh using CGAL... >> ERROR: CGAL error in CGALUtils::applyBinaryOperator difference: CGAL >> ERROR: >> assertion violation! Expr: itl != it->second.end() File: >> >> /data/OpenSCAD/libraries-mingw32-master/mxe/usr/i686-w64-mingw32.static/include/CGAL/Nef_3/SNC_external_structure.h >> Line: 1102 >> Geometries in cache: 8 >> Geometry cache size in bytes: 13645112 >> CGAL Polyhedrons in cache: 4 >> CGAL cache size in bytes: 97234272 >> Total rendering time: 0 hours, 1 minutes, 33 seconds >> Top level object is a 3D object: >> Simple: yes >> Vertices: 18712 >> Halfedges: 109364 >> Edges: 54682 >> Halffacets: 71950 >> Facets: 35975 >> Volumes: 2 >> Rendering finished./ >> >> mouthpiece_beak_v11.stl >> <http://forum.openscad.org/file/n15909/mouthpiece_beak_v11.stl> >> mouthpiece_outside_v11.scad >> <http://forum.openscad.org/file/n15909/mouthpiece_outside_v11.scad> >> mouthpiece_inside_v11.stl >> <http://forum.openscad.org/file/n15909/mouthpiece_inside_v11.stl> >> >> >> >> -- >> View this message in context: >> http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909.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 >> > >

According to Netfabb the mouthpiece inside has degenerate triangles. ​ On 27 January 2016 at 11:53, nop head <nop.head@gmail.com> wrote: > On second thoughts that shouldn't be a problem. Please can you attach the > STL for the outside. > > On 27 January 2016 at 11:48, nop head <nop.head@gmail.com> wrote: > >> Perhaps they intersect, so that although each mesh is manifold, the >> result isn't. >> >> On 27 January 2016 at 11:42, Johan Jonker <johangjonker@zonnet.nl> wrote: >> >>> *Already for weeks I am working on a configurable clarinet mouthpiece >>> design. >>> I make use of the sweep functions make the objects. >>> >>> I make three different stl files to keep the speed acceptable. >>> - The outside >>> - the inside >>> - the beak ; a part that is cut from the outside part too. >>> >>> The combination file looks like this:* >>> module mouthpiece () >>> { >>> difference()// body minus tafel >>> { >>> import("mouthpiece outside v11.stl"); >>> import("mouthpiece inside v11.stl"); >>> import("mouthpiece beak v11.stl"); >>> } >>> } >>> >>> *The problem is that combinations of the outside and the beak gives an >>> error >>> using F6. >>> I already check both objects with meshLab. The are allright. What can be >>> wrong?* >>> >>> *This is the output of the console:* >>> /Saved backup file: >>> >>> C:/Users/Eigenaar/Documents/OpenSCAD/backups/mouthpiece-backup-gqHp8304.scad >>> Compiling design (CSG Tree generation)... >>> Rendering Polygon Mesh using CGAL... >>> ERROR: CGAL error in CGALUtils::applyBinaryOperator difference: CGAL >>> ERROR: >>> assertion violation! Expr: itl != it->second.end() File: >>> >>> /data/OpenSCAD/libraries-mingw32-master/mxe/usr/i686-w64-mingw32.static/include/CGAL/Nef_3/SNC_external_structure.h >>> Line: 1102 >>> Geometries in cache: 8 >>> Geometry cache size in bytes: 13645112 >>> CGAL Polyhedrons in cache: 4 >>> CGAL cache size in bytes: 97234272 >>> Total rendering time: 0 hours, 1 minutes, 33 seconds >>> Top level object is a 3D object: >>> Simple: yes >>> Vertices: 18712 >>> Halfedges: 109364 >>> Edges: 54682 >>> Halffacets: 71950 >>> Facets: 35975 >>> Volumes: 2 >>> Rendering finished./ >>> >>> mouthpiece_beak_v11.stl >>> <http://forum.openscad.org/file/n15909/mouthpiece_beak_v11.stl> >>> mouthpiece_outside_v11.scad >>> <http://forum.openscad.org/file/n15909/mouthpiece_outside_v11.scad> >>> mouthpiece_inside_v11.stl >>> <http://forum.openscad.org/file/n15909/mouthpiece_inside_v11.stl> >>> >>> >>> >>> -- >>> View this message in context: >>> http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909.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 >>> >> >> >

Interesting, according to Meshlab its OK. How do I show that in NetFabb? -- View this message in context: http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909p15913.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Just click on the red cross button. On 27 January 2016 at 12:17, Johan Jonker <johangjonker@zonnet.nl> wrote: > Interesting, according to Meshlab its OK. How do I show that in NetFabb? > > > > -- > View this message in context: > http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909p15913.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 >

Ah, yes I see that. I wonder what can cause that kind of errors. It is just a hull of a cylinder and a rotated polyhedron. Is there anything I should take car of combining that? -- View this message in context: http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909p15915.html Sent from the OpenSCAD mailing list archive at Nabble.com.

It is caused by vertices so close together in one dimension that the triangle collapses into a line or a point when its vertices are converted to floats. OpenScad should fix when exporting STLs but as yet it doesn't. The only way to avoid it is to avoid very close vertices. E.g. don't have things meeting tangentially, overlap a bit, etc. I can be tricky if you mix vertices created in 2D with ones created in 3D as they can be slightly difference numerically. On 27 January 2016 at 12:32, Johan Jonker <johangjonker@zonnet.nl> wrote: > Ah, yes I see that. > > I wonder what can cause that kind of errors. > It is just a hull of a cylinder and a rotated polyhedron. > > Is there anything I should take car of combining that? > > > > -- > View this message in context: > http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909p15915.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 >

OK, thanks! that's a usefull suggestion. It gives an idea where I can fix the design. -- View this message in context: http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909p15917.html Sent from the OpenSCAD mailing list archive at Nabble.com.

It helps when I limit the $fn for some shapes. Now Nettfabb shows no errors anymore. OpenScad still gives errors. -- View this message in context: http://forum.openscad.org/CGAL-errors-when-combining-two-correct-STL-s-tp15909p15918.html Sent from the OpenSCAD mailing list archive at Nabble.com.