[vtkusers] which vtk classes to use?

Thu Feb 19 17:39:02 EST 2004

Hi Lisa,
  yes you are right. Actually the points will be at the quad corners, so
the scalars would be associated with the points which is the usual
situation, ie point data, rather than the less common cell data.
But there is no need for 'images' and textures (unless you really wanted an
'image' output), less is more...
    Dave

                      "lisa hughes"                                                                            
                      <lost_bits1110 at ho        To:       David.Pont at forestresearch.co.nz, vtkusers at vtk.org     
                      tmail.com>               cc:                                                             
                                               Subject:  RE: [vtkusers] which vtk classes to use?              
                      20/02/2004 10:46                                                                         

Hi David,
Thanks for your reply,
So when I create vtkStructuredPoints with dimensions that match the plane
resolution, will each point be at the center of each quadrilateral created
by vtkPlaneSource? If not, cant I just traverse the quadrilaterals
themselves and generate my spherical set of points - find my average
velocity - and then associate this scalar velocity value with that
particular quadrilateral cell to color in the cell?
Why do i need to use vtkTexture?

Also, do you think its better to use vtkImageData instead of
vtkStructuredPoints (in the vtk book it says that they will be phasing out
vtkStructuredPoints ..?)

Thanks again! I truly apprecieat it,
lisa

>Or you could just sample your field 'on the fly' using the probe filter
>concept:
>Create a vtkPlaneSource, place it with SetCentre, SetNormal, use
>SetXResolution and SetYResolution to suitable values (probably quite high)
>for sampling your 'field'.
>Create a vtkStructuredPoints with dimensions matching the plane
resolution.
>Traverse the points in the plane, at each point generate your spherical
set
>of random points, calculate the average velocity value and insert this
>value (may need manipulation) into the structured points at the
appropriate
>location.
>Create a vtkTexture and set the structured points as input.
>Pass the plane to a mapper, then actor, apply the texture to the plane
with
>actor->SetTexture.
>This should give an 'image' of the velocity field pasted onto the plane.
>There are probably alternatives that output data sets other than
structured
>points, eg polydata.
>
>   Dave Pont
>
>
>
>
>                       "lisa hughes"
>                       <lost_bits1110 at ho        To:       vtkusers at vtk.org
>                       tmail.com>               cc:
>                       Sent by:                 Subject:  RE: [vtkusers]
>which vtk classes to use?
>                       vtkusers-admin at vt
>                       k.org
>
>
>                       20/02/2004 08:05
>
>
>
>
>
>
>
>so basically I just need an idea for the pipeline...
>
>Thanks again ,
>lisa
>
>
> >
> >Hey vtkusers,
> >
> >Say I already have a 3D unstructured mesh
> >
> >and I have generated points which I seed within this mesh via a random
> >gaussian generator of spherical shape.  So basically i have a bunch of
> >'spheres' at various locations (inside my 3D mesh), and inside of each
> >sphere are points that have been randomly generated.   Then for each
>sphere
> >I have one scalar value associated with it (say an average velocity
value
> >of all the points that were contained within that one sphere)
> >
> >and I would also like to slice through the mesh according to some normal
> >and then color code the sliced mesh according to velocity info I have
>(via
>
> >those random points within each sphere location)
> >
> >So far, I was able to just color code just the points that I've seeded,
>so
>
> >basiclaly u just see a bunch of discrete points, of some color, within
my
> >3D mesh (i didint slice it yet)
> >
> >but say i want each of my 'spheres' to take up 1 mm squared of my screen
>(i
> >dont know how many pixels that would be?) and  i want to color-in those
>set
> >of pixels according to that single scalar value associated with that
>sphere
> >
> >how can i represent this?
> >glyphs?? i have no clue where to start at this point!
> >thanks in advance!! any help is truly appreciated
> >
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