[vtkusers] Overlay of 3D lines

David Netherway david.netherway at adelaide.edu.au
Thu Oct 24 01:29:18 EDT 2002


I wish to overlay lines defined in 3D on top of a VolPro generated 3D CT
reconstruction. The depth of the image from the VolPro card is probably a
fixed depth of 0. The lines that pass behind the z = 0 plane are not drawn.
I wish to draw them as if to an overlay plane, i.e. force them to be drawn
in front. Does anyone have a way of doing this without having to grab each
end point and the camera parameters, and then project onto the near plane
and render as 2D actors each time the camera is altered? Perhaps there is
way to directly send openGl drawing instructions to the window so that the
lines are drawn after everthing else.

Thanks for any suggestions.

Cheers, David

----- Original Message -----
From: "Sherwood, P (Paul)" <P.Sherwood at dl.ac.uk>
To: <vtkusers at public.kitware.com>
Sent: Thursday, 24 October, 2002 12:59 AM
Subject: [vtkusers] Picking questions

> Hi All,
> I am a just starting with vtk and I am using it to
> represent molecules as atoms and spheres.
> I am just experimenting with picking and I am unsure how
> to efficiently work out which atom was picked. I am
> working in Python.
> I can identify the picked property (Actor) using
> picker.GetPath().GetFirstNode(), by I am not sure of the best
> way to find out which atom in my model was picked. Is
> there a user data component of an actor I could set
> when it is created and access to indicate what it
> represents when it is picked?
> I notice the document to SetPickMethod for a property
> indicates that a function and an argument can be stored for
> each actor, this would enable me to use the argument as
> a way to work back from the actor to the originating object.
> However, it seems that in the python binding SetPickMethod
> only takes a single argument (the method itself).
> As far as I can see I would otherwise need to implement some
> look up process ( e.g. keep a dictionary relating each actor
> address to the chemical object that it relates to),
> but for a very long list of actors this seems rather
> inelegant and maybe slow.
> Also,  is there any way to pick multiple actors using something
> like the rubberband selection tools many programs use these days?
> Is there another way?
> thanks
> Paul Sherwood
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