[vtkusers] Speed of zoom

[James C. Robinson]

Fred,

Many thanks. There are two main styles of interactor (Trackball and
Joystick). I am using the trackball already. The "problem" is more
subtle/complex than that. It is related (see Lisa's e-mail reply to me) to
the fact that the zoom control (in trackball mode) using mouse movement is
gauged relative to the focal point position. As you get closer to the
camera's focal point, the zoom rate slows down. The problem with this is the
user (of the software, not the library) isn't aware of the camera's focal
point position (or probably even that he is using a "camera") and thus the
zoom rate apparently slows down for no reason depending on your "angle of
attack". The suggestion was to use "dolly" (which effectively factors the
camera's view angle, thus giving the equivalent of a physical camera's zoom
as opposed to increasing the detail by moving closer). This is not desirable
for my purposes.

Thanks again anyway,

Regards,

Jim

______________________

James C. Robinson, PhD,
Chartered Engineer,
Kepler Simulation Systems Ltd.,
42 Rivergrove,
Glanmire, Co. Cork,
Eire

Tel:         +353-21-4822028
Tel:         +353-87-2393010
Fax:        +353-21-4822028
E-mail:     j.robinson at kepler-systems.com
______________________

-----Original Message-----
From: Fred Pimbert [mailto:moi_the_fred at hotmail.com]
Sent: 22 April 2004 10:48
To: j.robinson at kepler-systems.com
Subject: RE: [vtkusers] Speed of zoom

you can add a style t othe vtkRenderWindowInteractor to control the mouse's
clics better. It is just something like this:

vtkInteractorStyleTrackballCamera *style =
vtkInteractorStyleTrackballCamera::New();
iren->SetInteractorStyle(style);

I hope that what I said will help you


>From: "James C. Robinson" <j.robinson at kepler-systems.com>
>Reply-To: <j.robinson at kepler-systems.com>
>To: "Vtk Users" <vtkusers at vtk.org>
>Subject: [vtkusers] Speed of zoom
>Date: Wed, 21 Apr 2004 16:25:48 +0100
>
>Dear All,
>
>I may have posted this query already (as it is an ongoing wish list
>member).
>I refer to the use of the mouse for zooming, panning etc. in a window.
>Sometimes, for reasons I have not quite figured out (although I suspect it
>has something to do with either the position of the camera focal point or
>the object origin) the zoom capability (or pan) slows down such that a
>large
>movement in the mouse cursor position results in a very small change (zoom
>or pan) on the view. That is, I might be zoomed in to a certain distance
>from an object (or detail of an object) and, depending on "how" I zoomed
>in,
>the subsequent zoom power can vary from strong to very slight.
>
>Has anybody (a) any idea what I am talking about and (b) any suggestions as
>to what is going on and what one can do to control this apparently (though
>I
>am sure it is not) arbitrary behaviour. NB: I cannot find any detailed
>reference to the interactor type control involved here in the doc (it
>refers
>only to "dolly" etc. when explaining zooming).
>
>Many thanks,
>
>Jim
>
>______________________
>
>James C. Robinson, PhD,
>Chartered Engineer,
>Kepler Simulation Systems Ltd.,
>42 Rivergrove,
>Glanmire, Co. Cork,
>Eire
>
>Tel:         +353-21-4822028
>Tel:         +353-87-2393010
>Fax:        +353-21-4822028
>E-mail:     j.robinson at kepler-systems.com
>______________________
>
>
>
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