[Paraview] qvtk problems with the pipeline

[Dominik Szczerba]

Clinton Stimpson wrote:
> On 08/01/2009 05:01 AM, Dominik Szczerba wrote:
>> Many thanks for the feedback. Pls see below:
>>
>> Clinton Stimpson wrote:
>>> Dominik Szczerba wrote:
>>>> My pipeline works all right and gets updated on demand properly. I 
>>>> achieve it by connecting spinboxes/lineedits etc. to functions that 
>>>> set parameters of my filters before I explicitly hit the final 
>>>> 'apply' button. The annoying problem is that the pipeline gets 
>>>> executed also when I interact with the render window (click to 
>>>> rotate etc.). I did not (intend to) set up such functionality, I 
>>>> want the pipeline to execute only after an explicit button click 
>>>> (like in paraview). How do I find out who is triggering the pipeline 
>>>> behind my back?
>>>>
>>>> - Dominik
>>>>
>>> ParaView queues up the changes, and only applies them to the filters 
>>> when the apply button is pressed.
>>> If you're applying them on the filters when spinboxes/lineedits 
>>> change, and a menu comes and goes over the graphics view, that could 
>>> trigger an update you might not want.
>>>
>>> How about your apply button gathering the parameters from the widgets 
>>> on the form and applying them?
>> That was my original idea and implementation: However, this way the 
>> WHOLE pipeline ALWAYS gets re-executed. Concrete example pipeline: 
>> extractVOI->GaussianSmooth. If Apply button gathers the parameters and 
>> sets them to the filters every time, changing e.g. only smoothing 
>> params (while keeping the same VOI) still causes both filters to 
>> re-execute. This should not happen, as VOI should be up to date. The 
>> same is true for more filters, e.g. Threshold: re-feeding the same 
>> parameters and/or arrays to process somehow fools the up-to-date'ness 
>> of the filter. Am I expected to walk around the problem by bookkeeping 
>> the changing params and the up-to-date'ness myself?
>>
>> Note that this is different to paraview, where you have only one 
>> filter per menu entry and can explicitly request changes. Here I have 
>> one meta-filter, consisting of several atomic ones.
>>
>> After your remark I feel the original approach was the right one. But 
>> then how do I only request the update if a REAL CHANGE and not only a 
>> FORMAL SET of parameters is the case?
>>
> 
> vtkSetMacro checks for changes before calling this->Modified();  But are 
> you saying its a problem because not all Set functions check for changes?

I am saying that (e.g.) setting VOI in vtkExtractVOI or 
InputArrayToProcess in vtkThreshold to the already previously set values 
(no factual change, just re-feed of the old ones) triggers the pipeline 
to re-execute. I do not understand this behavior as I was - as you point 
out - hoping for the set macros to take care of that.

> 
> To do your own bookkeeping, one idea is to connect to the QWidget's user 
> property's notify signal (see QMetaObject::userPropery), and anytime one 
> of those fires, you add to a list of widgets that have changed.  Then at 
> apply time, just push those values down.
> 

A little above my knowledge level but many thanks for the pointers to 
start with!

Overall, many thanks for valuable insights.

-- Dominik

> Clint
> 
> 


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