Re: [Visualpython-users] Control camera zoom?

[Bruce S. <Bru...@nc...>]

Could you describe briefly what it is that you want to do?

Bruce Sherwood

Craig Berry wrote:
> Okay, I stayed up way too late last night (er, this morning)
> experimenting with vpython camera view-distance control, and have come
> to the following conclusions (all relative to a scene containing a
> fixed set of static objects):
>
> 1. There are two fundamental parameters involved:
>       eyeDistance = mag(scene.mouse.camera - scene.center)
>       range = scene.range
>
> 2. eyeDistance can only be changed via user zooming, using
> mouse-middle dragging.  Nothing the program does directly ever changes
> it.
>
> 3. range can only be changed by the program.  Nothing the user does
> ever changes it.
>
> This seems wildly counterintuitive, and I wasted a lot of time trying
> to violate point 2 or 3.  But all this seems quite solid.
>
> So, as in your movecamera.py example, the only way to move the eye to
> a known apparent viewpoint following user-induced changes to
> eyeDistance is to change range proportionately, so that the two change
> cancel out.
>
> Is that a fair summary?  Or am I missing something?  And if any
> vpython developers are listening, why isn't there a programmatic way
> to change eyeDistance directly, as for other camera parameters like
> "forward"?
>
>