[Paraview] Is the VIEW-UP vector updated automatically?

[Kazuyoshi Furutaka]

Could someone tell me whether the meanings of the azimuth and
the elevation in ParaView the same as those in VTK (or "The
Visualization Toolkit" book, 4th ed.) or not?

In the book it reads:
"Changing the \textit{azimuth} of a camera rotates its position
around its view up vector, centered at the focal point.  Think
of this as moving the cmaera to the left or right while always
keeping the distance to the focal point constant.  Changing a 
camera's \textit{elevation} rotates its position around the cross
product of its direction of projection and view up centered at the
focal point.  This corresponds to moving the camera up and down.
To \textit{roll} the camera, we rotate the view up vector about
the view plane normal.  Roll is sometimes called twist."

I sometimes observe that (in the Multi Slice view,) Azimuth()
"rolls" instead of moving the camera left/right.

That's why I want to understand the geometry of view-up, direction
of projection, and so on...

Kazuyoshi


From: Kazuyoshi Furutaka <furutaka.kazuyoshi at jaea.go.jp>
Subject: Re: [Paraview] Is the VIEW-UP vector updated automatically?
Date: Tue, 07 Oct 2014 08:57:30 +0900 (JST)

> I just want to write a Python macro to change/rotate the camera
> position using Azimuth() and Elevation().
> 
> In addition to the following:
> 
>> I'm observing a curious behavior of paraview.simple.Azimuth();
>> camera is NOT moving left/right.
> 
> I sometimes get the following message
> 
>  Warning: In /home/furutaka/work/ParaView/ParaView.git/VTK/Rendering/Core/vtkRenderer.cxx, line 1030
> vtkOpenGLRenderer (0xa702510): Resetting view-up since view plane normal is parallel
> 
> and am wondering how can the view-up be parallel to the view-plane
> normal...
> 
> My understanding is that the view-up is (always) perpendicular to
> the direction of projection (pointing upward of the computer display)
> and therefore parallel to the view-plane, so the view-up should always
> be normal to view-plane normal.
> Isn't the view-plane normal parallel to the direction of projection?
> Isn't the view-plane parallel to the front/back clipping planes?
--
Kazuyoshi Furutaka
furutaka _dot_ kazuyoshi _at_ jaea _dot_ go _dot_ jp