[vtkusers] vtkXYPlotActor (SOLVED...sort of)

[Justin Giles]

Well, I figured out my problem.  When wanting to convert between
mouse/viewport X/Y coordinates you need to do the following:

vtkRenderWindowInteractor* iren =
vtkRenderWindowInteractor::SafeDownCast(obj);
   int event_pos[2];
   iren->GetEventPosition(event_pos); //generates X/Y coordinates based on
viewport where 0,0 is bottom left of window
   plot->SetViewportCoordinate(event_pos[0], event_pos[1]);  //sets the
coordinates you want converted
    plot->ViewportToPlotCoordinate(renderer);  //converts the coordinates
into plot coordinates
   double pos2[3];
   plot->GetViewPortCoordinate(pos2);  //retrieves the newly created plot
coordinates.


My new problem is the following:
When I have few x-axis data points (ie: 1-1000), the accuracy of the
coordinate conversion is very good, however when the number of data points
grows to 300000 or more, the accuracy is horrible.  Also, if I resize the
window, the accuracy is bad.  Any ideas?  Or is this normal?

Thanks,

Justin



On Fri, Feb 27, 2009 at 1:16 PM, Justin Giles <jtgiles at gmail.com> wrote:

> Thanks for the link, but I can't seem to get vtkPointPicker to work the the
> 2D XYPlotActor data correctly.  I feel that I'm missing something dealing
> with the mapping of my polydata set to the viewport coordinates correctly
> (or vice-versa).
>
> My input data is of the following format:
>
> x = 0-100 (integer values)
> y = 0-1 (floating point values)
>
> Those get placed into my polydata structure as points and scalars
> respectively.  I then add this dataset to the XYPlotActor.  I've played
> around with the polydatamapper2d, but I don't understand it very well
> evidently.
>
> When I click the mouse over one of the points in my plot, I'm able to
> extract the viewport x,y coordinate of the mouse from the windowinteractor.
> Then, using vtkPropPicker I'm able to pull out the point that was clicked on
> and get the x,y,z coordinates of the point picked by using
> picker->GetPickedPosition().  That gives me +- values between -1 and 1.
> What I am missing is how to map those values to find the point ids in my
> polydataset.
>
> Any further thoughts?  Do I need to add a mapper?  Do I need to play with
> vtkCoordinate on the dataset?  I'm basically at a loss...
>
> Thanks,
>
> Justin
>
>
> On Thu, Feb 26, 2009 at 4:23 PM, Shakes <Shekhar.Chandra at sci.monash.edu.au
> > wrote:
>
>> Hi Justin,
>>
>> This link might help, not for XY Plot class but for picking values from
>> the renderer by Mark Wyszomierski.
>>
>> <
>> http://devsample.org/index.php?option=com_content&task=view&id=48&Itemid=27
>> >
>>
>> Its got iren->GetEventPosition(event_pos) stuff, uses the Picker class.
>> Let me know how u go.... I will probably need to do this later. ;)
>>
>> HTH
>> Cheers
>> Shakes
>>
>> Justin Giles wrote:
>>
>>> Can anyone tell me how ViewportToPlotCoordinate is supposed to work?  No
>>> matter what I do I keep getting X = -25.8051 and Y = -0.167051.
>>>
>>> What I do when the mouse is clicked is the following:
>>> (plot is my vtkXYPlotActor object, renderer is my vtkRenderer object)
>>> -----------------------
>>>    vtkRenderWindowInteractor* iren =
>>> vtkRenderWindowInteractor::SafeDownCast(obj);
>>>    int event_pos[2];
>>>    iren->GetEventPosition(event_pos); //generates X/Y coordinates based
>>> on viewport where 0,0 is bottom left of window
>>>    plot->SetViewportCoordinate(event_pos[0], event_pos[1]);
>>>    double pos2[3];
>>>     plot->ViewportToPlotCoordinate(renderer, pos2[0], pos2[1]);
>>>
>>> //cout always shows -25.8051 and -0.167051
>>>    cout << pos2[0] << " : " << pos2[1] << endl;
>>> -------------------------------
>>>
>>> Any thoughts on this?  Am I doing something wrong?  My assumption on how
>>> this should work is that I would get coordinates based on the X/Y axis of
>>> the actual 2D plot.
>>>
>>> I've been stuck on this for quite a few days, so any help would be
>>> appreciated.
>>>
>>> Thanks,
>>>
>>> Justin
>>>
>>>
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