[vtkusers] Speed of zoom

[Lisa Avila]

Hello Jim,

Yes - you can move the focal point along with the camera position. Have a 
look at the vtkInteractorStyleFlight - it does something along these lines.

Lisa


At 04:44 PM 4/21/2004, James C. Robinson wrote:
>Lisa,
>
>Many thanks for the tip. The problem in using the view angle is exactly that
>to which you alluded.... the position of the viewer (camera) in the space. I
>assume that the implication is that if the camera is turned left or right,
>the viewer would not, in fact, have moved from his/her position (and thus,
>if moving through a scene, the user, in changing the camera viewing angle,
>would have had the impression of moving along a line further into the scene,
>but in fact would effectively have used a zoom analogous to using a real
>camera zoom).
>
>Is it not possible to either (a) invoke a method that ensures that the focal
>point is always suitable far away from the camera or (b) set the focal point
>to a position that is far enough away from the camera that it is never an
>issue (I assume that this is what happens when I "approach" my object from
>an angle such that the zoom slowdown is never an issue)?
>
>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: Lisa Avila [mailto:lisa.avila at kitware.com]
>Sent: 21 April 2004 17:54
>To: j.robinson at kepler-systems.com; Vtk Users
>Subject: Re: [vtkusers] Speed of zoom
>
>
>When you "zoom" by moving the camera closer / farther from the focal point
>(called "dolly") this will happen. The movement is a fraction of the
>current distance from the camera position to the focal point - hence when
>you get really close to the focal point you are only moving very small
>distances.
>
>An alternate way to "zoom" is to change the view angle - here you can get a
>smoother effect, but keep in mind that your camera doesn't actually move
>(which can be confusing when a user tries to navigate through the scene
>using your "zoom" functionality)
>
>Lisa
>
>
>At 11:25 AM 4/21/2004, James C. Robinson wrote:
> >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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