Hi all, thank you very very much for your help. It was very helpful for me. Now I know how to get on with my thesis. Maybe I find a working 3D Triangulator or I have to programm it by myself, because my aim is to triangulate also other solids and not only a sphere.
Agnes > > -------- Original-Nachricht -------- > Datum: Mon, 25 Oct 2010 15:42:59 +0100 > Von: Robert Osfield <[email protected]> > An: OpenSceneGraph Users <[email protected]> > Betreff: Re: [osg-users] Triangulate a pointcloud of a surface of a > sphere > > Hi Agnes, > > The osgUtil::DelaunayTriangulator uses a 2D projection for the > tessellation so is unable to tessellation point clouds whether there > are overhangs - such as a sphere. The osgUtil::Tessellator use GLU > tessellation, which also uses a 2D projection for it's tessellations. > > There aren't any tools in the OSG for tessellating a 3D point cloud, > so you with will need to find a 3rd party tool to tessellate your > points, or just work out how to do the tessellation directly yourself. > For the case of sphere you could probably come up with a technique > that knows that you are building a sphere and the structure of the > points to guide the tessellation. > > Robert. > > On Mon, Oct 25, 2010 at 3:15 PM, <[email protected]> wrote: > > Hi all, > > currently I am writing my bachelor's thesis and I am programming in > OSG. > > Consequently, I am a so-called newbie. > > > > Via 2 while-loops, which traverse the parametric representation of a > unit > > sphere around the origin, I receive supporting points. Singular points > are > > added manually. > > I want to triangulate these supporting points to approximate the > surface of > > a unit sphere. > > Therefore I pass a DelaunayTriangulator object my pointcloud (ca. > 400points) > > and call its triangulate() method. > > > > However, only the lower hemisphere is always triangulated. I tried to > > translate the parametric representation, along the positive z-axis so > that > > there are no negative values for the coordinates. Even this does not > change > > the result. > > I also tried to change the traversal of both for-loops but this did not > > produce other results ,too. > > > > At division of my pointcloud in two clouds (each ca. 400 points), one > for > > the lower and the other for the upper hemisphere, the triangulation > works > > without any problems. > > > > Does anybody know the reason for my problem, or what am I doing wrong? > > > > My code: > > > ---------------------------------------------------------------------------------------------------------- > > > > geom= new Geometry(); > > objGeode_ = new Geode(); > > objGeode_->addDrawable(geom); > > objGeode_->setNodeMask(objGeode_->getNodeMask() & > (~Isect::Intersection) > > & (~Isect::Pick)); > > rootNode->addChild(objGeode_); > > > > //--------------------- array of > > vertices--------------------------------- > > int numVertices = 20; > > double firstA = 0.0; > > double firstB = 0.0; > > double radian = 1.0; > > int counterA; > > int counterB; > > > > Vec3Array *vecTriangArray = new Vec3Array; > > > > //singular points > > vecTriangArray->push_back(Vec3(0.0, 0.0, 1.0)); > > vecTriangArray->push_back(Vec3(0.0, 0.0, -1.0)); > > > > //Traverse the latitude then along the meridian > > counterA = 1; > > firstA =(PI / numVertices)*counterA; > > > > while(firstA < PI){ > > counterB = 0; > > firstB = 0.0; > > > > while(firstB < 2*PI){ > > double x = radian * sin(firstA) * cos(firstB); > > double y = radian * sin(firstA) * sin(firstB); > > double z = radian * cos(firstA); > > vecTriangArray->push_back(Vec3(x, y, z)); > > counterB++; > > firstB = (2*PI / numVertices)*counterB; > > } > > counterA ++; > > firstA =(PI / numVertices)*counterA; > > } > > > > geom -> setVertexArray(vecTriangArray); > > > > //---------------Delaunay Triangulator------------- > > DelaunayTriangulator *trig = new DelaunayTriangulator(); > > trig -> setInputPointArray(vecTriangArray); > > > > //triangulate the points an add them to the primitive set > > trig->triangulate(); > > geom->addPrimitiveSet(trig->getTriangles()); > > > > > ---------------------------------------------------------------------------------------------------------- > > > > Thank you, > > > > Agnes > > > > > > -- > > Neu: GMX De-Mail - Einfach wie E-Mail, sicher wie ein Brief! > > Jetzt De-Mail-Adresse reservieren: http://portal.gmx.net/de/go/demail > > _______________________________________________ > > osg-users mailing list > > [email protected] > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > -- GMX DSL Doppel-Flat ab 19,99 €/mtl.! Jetzt auch mit gratis Notebook-Flat! http://portal.gmx.net/de/go/dsl
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