Thanks Lars,<br><br>I will go through it.<br><br>Jothy<br><br><div class="gmail_quote">On Mon, Jan 18, 2010 at 10:04 PM, Lars Friedrich Lars <span dir="ltr"><<a href="mailto:lars-friedrich@gmx.net">lars-friedrich@gmx.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Hi,<br>
<br>
what kind of objects do you have? Poly data or image data (volumetric data)?<br>
<br>
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.<br>
<br>
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'.<br>
<br>
regarding (B): Have a look at this posting <a href="http://old.nabble.com/3D-surface-to-2D-silhouette-to26642059.html#a26642059" target="_blank">http://old.nabble.com/3D-surface-to-2D-silhouette-to26642059.html#a26642059</a> where 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.<br>
<br>
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:<br>
- Convert the 3D poly data to a 3D (most simple: binary) image, e.g. using vtkSampleFunction, vtkImplicitDataSet<br>
- 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)<br>
- apply a vtkContourFilter to the generated 2D-projection (frame buffer image) and extract the 2D poly data contour(s)<br>
<br>
regards,<br>
lars<br>
<br>
<br>
-------- Original-Nachricht --------<br>
> Datum: Mon, 18 Jan 2010 15:15:17 +0000<br>
> Von: KS Jothybasu <<a href="mailto:jothybasu@gmail.com">jothybasu@gmail.com</a>><br>
> An: <a href="mailto:vtkusers@vtk.org">vtkusers@vtk.org</a><br>
> Betreff: [vtkusers] projection onto a plane<br>
<div><div></div><div class="h5"><br>
> Hi all,<br>
><br>
> I am trying to projects the objects on to a plane that is at a known<br>
> distance from the camera/ source.<br>
><br>
> Let me explain further<br>
><br>
> you have your eye at 0cm and you have an aperture before your eye at 50cm,<br>
> if you view through the aperture the objects below the aperture will<br>
> appear.<br>
> I want to projeect these objects on to a plane lets say, 80 cm.<br>
><br>
> How to do that?<br>
><br>
> Thanks<br>
><br>
> Jothy<br>
<br>
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