[vtkusers] Picking invisible object...vtkPlane ( Simpleversion ! )

[Sebastien Auclair]

I agree that i could miss the plane if the view plane and the vtkPlane are
perpenticular but this isn't the problem here. (We are managing this last
case)

It behaves like if the vtkPlane was always placing himself parallel to the
display plane before shooting (i.e. When ProjectPoint is called)
Maybe someone from Kitware could confirm that !

Bottom line, if i display a small sphere at the retured coordonates
(vtkPlane::ProjectPoint), it will not be under the mouse cursor. It should
be !
I also understand that the returned coordonate can be outside the clipping
planes but this isn't the problem here.

Thanks for any help !
________________________________
Seb

----- Original Message -----
From: "Charl P. Botha" <c.p.botha at ewi.tudelft.nl>
To: "VTK Users List" <vtkusers at vtk.org>
Sent: Tuesday, July 22, 2003 8:29 AM
Subject: Re: [vtkusers] Picking invisible object...vtkPlane ( Simpleversion
! )


> On Tue, 2003-07-22 at 14:14, Sebastien Auclair wrote:
> > The vtkPlane's normal is not always parallel to the display plane's
normal.
> > In which case the returned value (vtkPlane::ProjectPoint) is always
correct.
> > The more perpenticular the vtkPlane's normal is in relation to the
Display
> > plane's normal, the less accurate the intersection coordinates becomes.
(It
> > should be the opposite !)
>
> Why?  The more perpendicular the vtkPlane's normal is to the view plane
> normal, the more perpendicular the vtkPlane is to the view plane, which
> means that your projection point will shoot off to infinity or miss the
> plane completely.
>
> You're probably going to have to solve this problem by yourself by
> analysing the source code and first manually doing the math that is
> being implicitly performed by your VTK calls to see where your
> understanding and the code diverge.
>
> --
> charl p. botha http://cpbotha.net/ http://visualisation.tudelft.nl/
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