[vtkusers] VTK stops rendering during animation after interaction

[Eduardo Kortright]

Hello,

I am having a problem when doing a simple animation using Tcl by 
manipulating the camera to change the view of a scene.  I have a simple 
for loop doing things like changing the azimuth by one degree, or pitch 
or roll, etc.  This should give a smooth motion of the camera, and it 
always begins to show a smoothly changing scene.

However, under certain circumstances, after a few dozen frames the 
render window simply stops rendering.  It is as though it thinks the 
render requests are coming in too fast and it simply gives up.  After 
that, it only renders at the end when the loop finishes, showing the 
final position of the camera.

I have narrowed the problem down to this: if one manually changes the 
position of the camera using a render window interactor by clicking with 
the mouse, then calling the animation sequence immediately afterward 
produces the interrupted effect.  Calling the animation sequence 
*without* having used the interactor does not result in the 
interruption.  So, if I want to position the camera with the interactor, 
I have to use the mouse, then call the animation sequence (with the 
animation being interrupted until the loop finishes), and then I have to 
call the animation sequence again immediately and it will render every 
frame for the entire duration of the loop. 

By the way, changing the position of the camera by calling one of the 
camera methods from the command line does not produce the interruption 
in the animation. loop.  It is as though the interactor sets some flag 
that limits the number of frames to render before quitting; when the 
flag is cleared, the rendering does not get interrupted.

Finally, I have tested this in Windows XP with various graphics cards 
supporting OpenGL, all with the same result.  I have tried VTK 4.2 
straight from the User's Guide CD ROM, and also a version of VTK 4.4 
compiled with MS VC++ 7.0 with the same result.

I will be grateful for any information about how to prevent this from 
happening.

-- 
Eduardo Kortright                         Department of Computer Science
eduardo at cs.uno.edu                        University of New Orleans
Phone: (504) 280-6626                     Lakefront Campus
Fax:   (504) 280-7228                     New Orleans, LA 70148