[vtkusers] projection onto a plane

[KS Jothybasu]

Thanks Lars,

I will go through it.

Jothy

On Mon, Jan 18, 2010 at 10:04 PM, Lars Friedrich Lars <
lars-friedrich at gmx.net> wrote:

> Hi,
>
> what kind of objects do you have? Poly data or image data (volumetric
> data)?
>
> If you had image data, you could simply set up a camera according to your
> projection requirements, and use a volume mapper to generate the desired
> projection (on a virtual image plane). E.g. a maximum intensity projection
> or something like that would generate the 'aperture'-like projection.
>
> If you had poly data, the task might be a bit more complicated (at least to
> my knowledge) especially depending on whether you need the generated
> 2D-projection of the 3D-object as (A) a (closed) 2D-contour (poly data) or
> (B) 'for visualization only'.
>
> regarding (B): Have a look at this posting
> http://old.nabble.com/3D-surface-to-2D-silhouette-to26642059.html#a26642059where vtkPolyDataSilhouette is used for generating an aperture-like poly
> data representation. NOTE: this filter is more or less for visualization
> purposes only as it does not map (and logically connect) the extracted edge
> (~lines) onto the virtual plane. Moreover, this filter will produce edges
> that do not really conform to a traditional 'silhouette' - there will occur
> interesting artifacts which are intuitionally not part of the silhouette.
> Generating real silhouettes (or aperture shapes) from pure 3D poly data will
> in general be very difficult, I think.
>
> regarding (A): Some weeks ago, I faced (and still do) this issue too. I did
> not write a pipeline to accomplish this, but I think the following
> approximate approach should be possible:
> - Convert the 3D poly data to a 3D (most simple: binary) image, e.g. using
> vtkSampleFunction, vtkImplicitDataSet
> - apply a volume mapper with the desired camera setup to the generated
> volume (e.g. with maximum intensity projection or a more efficient
> implementation - 'first voxel hit' or so)
> - apply a vtkContourFilter to the generated 2D-projection (frame buffer
> image) and extract the 2D poly data contour(s)
>
> regards,
> lars
>
>
> -------- Original-Nachricht --------
> > Datum: Mon, 18 Jan 2010 15:15:17 +0000
> > Von: KS Jothybasu <jothybasu at gmail.com>
> > An: vtkusers at vtk.org
> > Betreff: [vtkusers] projection onto a plane
>
> > Hi all,
> >
> > I am trying to projects the objects on to a plane that is at a known
> > distance from the camera/ source.
> >
> > Let me explain further
> >
> > you have your eye at 0cm and you have an aperture before your eye at
> 50cm,
> > if you view through the aperture the objects below the aperture will
> > appear.
> > I want to projeect these objects on to a plane lets say, 80 cm.
> >
> > How to do that?
> >
> > Thanks
> >
> > Jothy
>
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