[vtkusers] abnormal chart using scatter points

[Eric E. Monson]

Hello,

I really think this might just be a bug in VTK 5.6.1. As I said before, there has been a lot of development on the Charts API between 5.6 and now. Your code works fine for me with the VTK development head, and I don't have a 5.6 build lying around to test it on. I'm not sure why a LINE plot wouldn't have trouble with it, but POINTS does ¨C vtkPlotLine is a pretty bare-bones subclass of vtkPlotPoints.

So, I think your only options are to either pull the development version and build from the git repository, or wait for a little while for 5.8 to be released. (That should be very soon, but I haven't heard a fixed date.)

Sorry I couldn't be more help,
-Eric


On Mar 31, 2011, at 8:23 AM, liuxy wrote:

> Thank you for your help!!
> 
> The version of VTK I used is 5.6.1, and compile the source code with Cmake2.8 and VS 2008, the code of drawing scatter points more than 40,000  is that :
> 
> #include <vtkSmartPointer.h>
> #include <vtkChartXY.h>
> #include <vtkContextScene.h>
> #include <vtkContextView.h>
> #include <vtkFloatArray.h>
> #include <vtkShortArray.h>
> #include <vtkPlotPoints.h>
> #include <vtkRenderWindow.h>
> #include <vtkRenderWindowInteractor.h>
> #include <vtkRenderer.h>
> #include <vtkTable.h>
> #include <vtkAxis.h>
>  
> int main(int, char*[])
> {
>   // Set up a 2D scene, add an XY chart to it
>   vtkSmartPointer<vtkContextView> view = vtkSmartPointer<vtkContextView>::New();
>   vtkSmartPointer<vtkChartXY> chart = vtkSmartPointer<vtkChartXY>::New();
>   view->GetScene()->AddItem(chart);
>   chart->SetShowLegend(true);
> 
>   // Create a table with some points in it...
>   vtkSmartPointer<vtkTable> table = vtkSmartPointer<vtkTable>::New();
> 
>   // float Êý×é
>   vtkSmartPointer<vtkFloatArray> arrX =vtkSmartPointer<vtkFloatArray>::New();
>   arrX->SetName("X Axis");
>   table->AddColumn(arrX);
>   vtkSmartPointer<vtkFloatArray> arrC = vtkSmartPointer<vtkFloatArray>::New();
>   arrC->SetName("sin");
>   table->AddColumn(arrC);
>   
>   // amount of scatter points
>   int numPoints =40000;
> 
>   float inc = 7.5 / (numPoints-1);
>   table->SetNumberOfRows(numPoints);
>   for (int i = 0; i < numPoints; ++i){
>     table->SetValue(i, 0, i * inc);
>     table->SetValue(i,1, sin(i * inc));
>   }
>   
>   // Add multiple scatter plots, setting the colors etc
>   vtkPlot *points = chart->AddPlot(vtkChart::POINTS);
>   points->SetInput(table, 0, 1);
>   points->SetColor(0, 0, 255, 255);
>   points->SetWidth(2.0);
> 
>   //Finally render the scene
>   view->GetRenderer()->SetBackground(1.0, 1.0, 1.0);
>   view->GetRenderWindow()->SetSize(1024, 600);
>   view->GetInteractor()->Initialize();
>   view->GetInteractor()->Start();
>   return EXIT_SUCCESS;
> }
> 
> 
> and the run effect is like 4000error.jpg, if  I replace vtkChart::POINTS to vtkChart::LINE ,the result is right, why ?
>  
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 2011/3/28 Eric E. Monson <emonson at cs.duke.edu>
> Hello,
> 
> Which version of VTK are you using? I've definitely drawn scatter plots using the Charts API that had more than 40,000 points, and this is something the Charts are supposed to be good at, so it will be interesting to see what has gone wrong in your case. The VTK version is important because a lot of development has gone on in the Charts since 5.6, so if you're using 5.6 the bug may already have been fixed.
> 
> Otherwise, if you're using the development head and this is still happening, maybe you can pass along a minimal piece of code that demonstrates the problem and we can help figure out what's going on.
> 
> Talk to you later,
> -Eric
> 
> ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤ ¡¤
> Eric E Monson
> Duke Visualization Technology Group
> 
> 
> On Mar 28, 2011, at 1:43 AM, liuxy wrote:
> 
> > I used vtkChart API to draw a line: y=sin(x) using "scatter points",
> >
> > the chart is abnormal when the number of points are more than 40,000.
> >
> > just like pictrue a.jpg in enclosure.
> >
> > but if the points are less than 40,000 or using "Line" to draw y=sin(x),
> >
> > the chart is correct. Just like pictrue b.jpg.
> >
> > I want to know how to use "scatter points" in drawing charts with huge scale of points ?
> >
> > or vtkChart may be not applicable in this situation ?
> >
> >
> > P.S:
> >
> > By reading the source Code of vtkChart,
> >
> > I found when drawing in "scatter points",
> >
> > it used function 'DrawPointSprites'.
> >
> > if replaced it with function 'DrawPoints',the chart shows correctly,
> >
> > even number of points more than 40,000.
> > <a.JPG><b.JPG>_______________________________________________
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> 
> <40000error.JPG>

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