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Adjusting Trackball Radius
| Adjusting Trackball Radius [message #55303] |
Thu, 16 August 2007 00:55 |
Gaurav
Messages: 50
Registered: January 2007
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Adjusting Trackball Radius:
My query is: Can a mathematical formula be derived to relate the
Trackball Radius of an object to the extent of the object visible
through the viewplane_rectangle?
What I am basically doing is to display a spherical object within the
view which can be zoomed upon by applying viewport transformations
i.e. varying the values in the viewplane_rectangle property of the
view. The user is then able to rotate the sphere by clicking and
dragging the mouse over the sphere. This is where the trackball and
its radius comes in. Right now I am manually adjusting the values of
the trackball radius depending upon the values of the
viewplane_rectangle. But this method is not working right as it is not
possible to define trackball radii for every conceivable values of the
viewplane extent. And if the radius is not adjusted properly, the view
pans too much or too little with respect to the desired extent. Is
there a mathematical way to relate the two(i.e. the view extent and
the trackball radius), knowing the extent of the view of the object
(through viewplane_rectangle keyword) and the size (in pixels) of the
draw widget that contains the view?
Thanks, in advance.
Gaurav
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