[vtkusers] VTK rendering pipeline - ray casting

[Karthik Krishnan]

Juan:

You would use the vtkVolumePicker (or even the vtkCellPicker, although it
ignores the cropping planes); not the prop picker, to pick the volume at a
given "opacity iso-surface". (SetVolumeOpacityIsoValue and
UseVolumeGradientOpacity)

It would have been better instead to do that based on the accumulated
opacity along the ray, until it reached a stopping opacity. I'll try to add
that at some point.

But you can pick volumes.

--
karthik

On Fri, Sep 30, 2011 at 6:20 PM, Juan Carlos Prieto <
prieto at creatis.insa-lyon.fr> wrote:

> **
> Hi Julien,
>
> Yes the 3D position, so I'm now using the vtkPropPicker, this picker will
> actually give me the world position in the actor where the hit occurred.
> I'm trying to solve another problem now. When I change the camera's
> position and view direction, the actor is not rendered unless I perform some
> interaction with the window (e.x. left click, zoom etc.), If I perform the
> pick then the result is empty.
>
> The idea is to find a set of intersections given a set of rays, so I don't
> know how to update the view with out the interaction.
>
> Is there a way to do this?
>
> Le 30/09/2011 14:03, Julien Finet a écrit :
>
> Hi Juan,
> if you use a cellpicker, keep in mind that the volume ray caster is under
> the hood a cube with 6 faces (technically, with 12triangular faces). So you
> always pick the bounds of the volume.
> Are you sure you are interested in the cell and not the 3D position ?
> julien.
>
> On Fri, Sep 30, 2011 at 7:38 AM, Juan Carlos Prieto <
> prieto at creatis.insa-lyon.fr> wrote:
>
>>  Hi Julien,
>>
>> Thank you very much for the presentation, I kept on looking and I saw that
>> using a vtkCellPicker might do the job of finding the intersection of a ray
>> against an actor in a renderer.
>> To do this, I'm moving the camera to look in the direction where I want
>> the intersection to happen, but it seems that after producing the pick, it
>> always finds the same cell in the actor.
>>
>> Can you give me some suggestion on how should I do this?
>>
>> Thank you very much
>>
>> Le 29/09/2011 20:22, Julien Finet a écrit :
>>
>> Hi Juan,
>>
>>
>>  You can find a GPU ray casting high level presentation in the Kitware
>> Source of October 2009:
>> http://www.kitware.com/products/archive/kitware_quarterly0708.pdf
>>
>>  Hth,
>> Julien.
>>
>> On Thu, Sep 29, 2011 at 11:54 AM, Juan Carlos Prieto <
>> prieto at creatis.insa-lyon.fr> wrote:
>>
>>>  Dear VTK Users,
>>>
>>> I was wondering if anyone can point me out to the documentation of the
>>> VTK rendering pipeline, I want to analyze how the ray casting is done as I
>>> came across a little problem where I need find the point of intersection in
>>> the surface.
>>>
>>> Thank you very much.
>>>
>>> --
>>> Juan Carlos Prieto
>>> Phd Student
>>> CREATIS <http://www.creatis.insa-lyon.fr> Tel:+33472438918
>>> 7 Av Jean Capelle
>>> 69621 Villeurbanne Cedex
>>> France
>>> Personal page <http://www.creatis.insa-lyon.fr/%7Eprieto>
>>>
>>> _______________________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
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>>> Please keep messages on-topic and check the VTK FAQ at:
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>>>
>>
>> --
>> Juan Carlos Prieto
>> Phd Student
>> CREATIS <http://www.creatis.insa-lyon.fr> Tel:+33472438918
>> 7 Av Jean Capelle
>> 69621 Villeurbanne Cedex
>> France
>> Personal page <http://www.creatis.insa-lyon.fr/%7Eprieto>
>>
>
>
> --
> Juan Carlos Prieto
> Phd Student
> CREATIS <http://www.creatis.insa-lyon.fr> Tel:+33472438918
> 7 Av Jean Capelle
> 69621 Villeurbanne Cedex
> France
> Personal page <http://www.creatis.insa-lyon.fr/%7Eprieto>
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
>
>
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