On Oct 25, 2010, at 10:42 AM, Robert Osfield wrote: > 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.
Agnes There are several software packages that will perform spherical delaunay here are a few links http://people.sc.fsu.edu/~jburkardt/m_src/sphere_delaunay/sphere_delaunay.html http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_3/Chapter_main.html#Section_37.2 http://www.qhull.org/html/qdelaun.htm Norman > > 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
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