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Re: reconstruction of 3D grid with connectivity

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91418] Re: reconstruction of 3D grid with connectivity
  • From: Narasimham <mathma18 at hotmail.com>
  • Date: Thu, 21 Aug 2008 04:14:26 -0400 (EDT)
  • References: <g8gj4j$etq$1@smc.vnet.net> <g8grao$ifa$1@smc.vnet.net>

On Aug 20, 3:23 pm, Jens-Peer Kuska <ku... at informatik.uni-leipzig.de>
wrote:
> Hi,
>
> a) your assumption "when u and v  are each incremented by given ustep
> and vstep" because ParametricPlot3D[] make a irregular triangle mesh
> you can see the mesh with
>
> plt=ParametricPlot3D[{Cos[phi]*Sin[th], Sin[phi]*Sin[th], Cos[th]},
>   {th, 0, Pi}, {phi, 0, 2 Pi}, Mesh -> All]
>
> b) the connectivity can be shown with
>
> GraphPlot[
>   Union[Flatten[(Rule @@@ Partition[#, 2, 1, {-1}]) & /@
>       Cases[plt, _Polygon, Infinity][[1, 1]] /. (a_ -> b_) /;
>        a > b :> (b -> a)]
>    ]]
>
> Regards
>    Jens
>
> Narasimham wrote:
> > For surface ParametricPlot3D[{x = f(u,v), y = g(u,v), z = h(u,v)},
> > {u,umin,umax,ustep},{v,vmin,vmax,vstep}]
>
> > how to obtain the connectivity matrix (when u and v  are each
> > incremented by given ustep and vstep), using Delaunay or Voronoi
> > triangulations? In this case there would be curved or skewed
> > quadrilaterals instead of triangles that discretizes the surface.When
> > connectivity matrix and coordinate matrix are given with each  point
> > ID reference number, the surface should be  reconstructed, i.e.,
> > plotted, and/or Shown without again giving out the above command.
>
> > Thanks in advance,
>
> > Narasimham

If p1,p2 etc are labels,  ( p1= {x1,y1,z1} ; p2 = (x2,y2,z2} ),
connectivity p1 -> p2 etc is required.

Narasimham


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