[vtkusers] Intersection point of a line with a Surface (vtkPolyData)

Chiang, Wen-Hsing wchiang at sspa.com
Wed Jan 23 16:18:57 EST 2002


Hi,
I think the following question could be very trivial, but I could not
find a solution.

Given a surface (an instance of vtkPolyData) and a spatially vertical
line [(x,y,-1E20)--(x, y, 1E20)], how can one calculate the z-coordinate
of the intersection point of the line and the surface?


Wen-Hsing Chiang
http://www.sspa.com



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Today's Topics:

   1. Re: Again, I am doing something wrong. (Mace.cxx) (Nick Edgington)
   2. splatting a sphere onto a 2D structure/image (stefano mininel)
   3. wxVTKWindow: controlling events. (stefano mininel)
   4. Re: Function Plots (Andy F. Miller)

--__--__--

Message: 1
From: "Nick Edgington" <OutOfTurn at Yahoo.com>
To: <vtkusers at public.kitware.com>
Subject: Re: [vtkusers] Again, I am doing something wrong. (Mace.cxx) 
Date: Wed, 23 Jan 2002 10:26:45 -0500

Just a quick comment:
     when I SetResolution(0) in the examples I posted  this is not
surprising, but I just thought I would note it.


 vtkConeSource *cone = vtkConeSource::New();
    cone->SetResolution(0);


void vtkGlyph3D::Execute()
{


........
numSourcePts = sourcePts->GetNumberOfPoints();  <<<==== Crashes
.......
}


----- Original Message -----
From: "Berk Geveci" <berkgeveci at hotmail.com>
To: <OutOfTurn at Yahoo.com>; <vtkusers at public.kitware.com>
Sent: Tuesday, January 22, 2002 10:06 AM
Subject: Re: [vtkusers] Again, I am doing something wrong. (Mace.cxx)


> Here is what happens: you get the input of the glyph
> filter and add a scalars array to it. This input is
> also the output of another source (in this case, a
> sphere source, as far as I can see). When the pipeline
> executes, sphere source initializes it's output before
> generating data and pufff your scalars are gone.
> Whatever you do, sphere source will initialize it's
> output everytime it runs. The simplest solution is this:
>
> Create a sphere source
> Update it
> Get it's output and severe it from the source
> (with SetOutput(NULL);)
> Add your scalars
>
> There other ways of doing this (some of which allow you
> to keep the source in the pipeline), if you want more hints,
> let me know.
>
> -Berk
>
>
> >From: "Nick Edgington" <OutOfTurn at Yahoo.com>
> >To: <vtkusers at public.kitware.com>
> >Subject: [vtkusers] Again, I am doing something wrong. (Mace.cxx)
> >Date: Tue, 22 Jan 2002 09:05:45 -0500
> >
> >     I am using Vtk40 under winnt.
> >
> >     I attach a scalar to a vtkGlyph3D
> >
> >
> >main(){
> >...........................
> >      scalars = vtkFloatArray::New();
> >
> >
> >       scalars->InsertTuple1(0, .5);
> >       scalars->InsertTuple1(1, .5);
> >       scalars->InsertTuple1(2, 1);
> >       scalars->InsertTuple1(3, 0);
> >       scalars->InsertTuple1(4, 1);
> >       scalars->InsertTuple1(5, 0);
> >
> >         ............
> >        vtkDataSet *input = glyph->GetInput();
> >       vtkPointData * pd = input->GetPointData();
> >       pd->SetScalars(scalars);
> >}
> >
> >When I trace through
> >
> >void vtkGlyph3D::Execute()
> >{
> >
> >         ...........
> >
> >         pd->GetScalars();      <<<<<===  returns NULL
> >                                           <<<<< === because
> >this->GetAttribute(SCALARS); returns -1
> >                                           <<<<<===  even thought it
was
> >originally set to 0 by the pd->SetScalars(scalars);
> >
> >I can force it to work by changing the flag myself.
> >
> >                     Thanks in advance
> >                             Nick Edgington
> >
> >
> >
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--__--__--

Message: 2
Date: Wed, 23 Jan 2002 16:34:51 +0100
From: stefano mininel <mininel.ml at gnbts.univ.trieste.it>
To: vtkusers at public.kitware.com
Subject: [vtkusers] splatting a sphere onto a 2D structure/image

Sorry, it's probably something asked already, but right now I'm stuck
and I need a helpful input/tip.
I want to probe electrical potential values upon a sphere and save
sphere surface as a 2D structure (image, structured points ...) like in
a 2D world map (with poles deformed).
My code
"
  vtkSphereSource *pSferaScalpoSource = vtkSphereSource::New();
    pSferaScalpoSource->SetRadius(8.5);
    pSferaScalpoSource->SetThetaResolution(180);
    pSferaScalpoSource->SetPhiResolution(179);
    pSferaScalpoSource->SetStartPhi(1);
    pSferaScalpoSource->SetEndPhi(179);

  vtk ProbeFilter *pSferaScalpoProbe = vtkProbeFilter::New();
    pSferaScalpoProbe->SetInput(pSferaScalpoSource->GetOutput());
    pSferaScalpoProbe->SetSource(pPotGrid);       // (pPotGrid:
vtkUnstructuredGrid holding the potential values)
"
works well for the probing but ... now? I feel lost in a maze of vtk
filters!!
Vtk used is 3.1.2. Compiler is VC++.
Any help or tip appreciated! Thanks in advance.

    Stefano Mininel


--__--__--

Message: 3
Date: Wed, 23 Jan 2002 16:52:15 +0100
From: stefano mininel <mininel.ml at gnbts.univ.trieste.it>
To: vtkusers at public.kitware.com
Subject: [vtkusers] wxVTKWindow: controlling events.

Stereo rendering with 2+ renderers in one window doesn't work correctly.
A solution is to remove temporarily all renderers except the one to be
put in 3D, and adding them again to the window when switching back into
2D. In my wxWindows/vtk application  my 2D/3D switch customized this way
works correctly.

The problem is: when "3" key is pressed this event calls the "regular"
vtk 2D/3D switch and vtkWindow goes into a buggy stereo rendering.

I tried to prevent further event processing by adding
" if (event.GetKeyCode == 33) return; " in
wxVTKWindow::OnKeyDown,
wxVTKWindow::OnKeyUp,
wxVTKWindow::OnChar
(trying all possible combinations!) but it seems I can't prevent vtk
from receiving the "3 key" event.
Any idea from one of the wxWindows/vtk users?
Thanks in advance for any help.

    Stefano Mininel


--__--__--

Message: 4
From: "Andy F. Miller" <aamiller at alumni.princeton.edu>
To: "Vtkusers at Public. Kitware. Com (E-mail)"
<vtkusers at public.kitware.com>
Subject: Re: [vtkusers] Function Plots
Date: Wed, 23 Jan 2002 08:33:51 -0800

This is a multi-part message in MIME format.

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If you don't mind a standalone program (i.e. not integrated with VTK), =
GNUPLOT (http://www.gnuplot.vt.edu/) is very easy to use.

Andy
  ----- Original Message -----=20
  From: Christopher R. Volpe=20
  To: Vtkusers at Public. Kitware. Com (E-mail)=20
  Sent: Tuesday, January 22, 2002 8:46 PM
  Subject: [vtkusers] Function Plots


  Is anyone using vtk to produce simple 2D function plots? I'm in need =
of
  doing some simple plotting, and if I can do it in vtk without a lot of
  wheel-reinventing, that would be great. (Conversely, if people have =
looked
  into this and decided that vtk is the wrong tool and found something =
better,
  I'd be interested to hear about it. Preferably something quick and =
dirty,
  not something expensive with a learning curve such as Matlab or
  Mathematica.) Thanks in advance.

  -Chris



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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2712.300" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>If you don't mind a standalone program
=
(i.e. not=20
integrated with VTK), GNUPLOT (<A=20
href=3D"http://www.gnuplot.vt.edu/">http://www.gnuplot.vt.edu/</A>) is =
very easy=20
to use.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Andy</FONT></DIV>
<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3Dcvolpe2 at nycap.rr.com =
href=3D"mailto:cvolpe2 at nycap.rr.com">Christopher=20
  R. Volpe</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dvtkusers at public.kitware.com=20
  href=3D"mailto:Vtkusers at Public. Kitware. Com =
(E-mail)">Vtkusers at Public. Kitware.=20
  Com (E-mail)</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, January 22, 2002
=
8:46=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [vtkusers] Function =
Plots</DIV>
  <DIV><BR></DIV>Is anyone using vtk to produce simple 2D function =
plots? I'm in=20
  need of<BR>doing some simple plotting, and if I can do it in vtk =
without a lot=20
  of<BR>wheel-reinventing, that would be great. (Conversely, if people =
have=20
  looked<BR>into this and decided that vtk is the wrong tool and found =
something=20
  better,<BR>I'd be interested to hear about it. Preferably something =
quick and=20
  dirty,<BR>not something expensive with a learning curve such as Matlab
=

  or<BR>Mathematica.) Thanks in=20
advance.<BR><BR>-Chris<BR><BR></BLOCKQUOTE></BODY></HTML>

------=_NextPart_000_0030_01C1A3E8.AFB6D6A0--



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