VTK/Charts

Goals

• Render 2D charts using OpenGL/VTK
• Scalable to large data sets
• Simple, flexible API
• Enable server side rendering of charts with VTK compositing
• Proper handling of IEEE Not-A-Number (NaN) values in plots of both experimental and simulation data.

Open Questions

• Alternate backend to produce publication quality output?
• Possibility to extend the API to 3D charts in the future?
• Maybe real-time charting? (just-in-time visualization of data sets)

Unlimited Options

Supported Parameter Types

• Basic types (double, int, string, vtkVariant)

<source lang="cpp"> vtkDotMark* m = vtkDotMark::New(); m->SetParameter("size", 10); </source>

• Data object

<source lang="cpp"> vtkDirectedGraph* g = vtkDirectedGraph::New(); //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("data", g); </source>

• Pipeline output port

<source lang="cpp"> vtkRandomGraphSource* s = vtkRandomGraphSource::New(); //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("data", s->GetOutputPort()); </source>

• vtkArray

<source lang="cpp"> vtkDenseArray<double>* a = vtkDenseArray<double>::New(); //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("size", a); </source>

• vtkAbstractArray

<source lang="cpp"> vtkDoubleArray* a = vtkDoubleArray::New(); //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("size", a); </source>

• Data object + field type + array name

<source lang="cpp"> vtkTable* t = vtkTable::New(); //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("size", t, vtkDataObject::ROW, "columnName"); </source>

• Data object + field type + array name + component index

<source lang="cpp"> vtkTable* t = vtkTable::New(); vtkDoubleArray* loc = vtkDoubleArray::New(); loc->SetNumberOfComponents(2); //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("left", t, vtkDataObject::ROW, "location", 0); m->SetParameter("bottom", t, vtkDataObject::ROW, "location", 1); </source>

• Function pointer

<source lang="cpp"> double MySize(vtkMark* m, int i) { return 10*i; } //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("size", &MySize); </source>

• Functor (i.e. struct type with operator()) - requires SetParameter to be templated.

<source lang="cpp"> struct MySize {

 double operator()(vtkMark* m, int i) { return 10*i; }

} //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("size", MySize()); </source>

• Lambda function (boost::lambda)

• Parameter strategies

<source lang="cpp"> class vtkDoubleParameter {

 virtual double Get(vtkMark* m, int i) = 0;

}

class MySize : public vtkDoubleParameter { protected:

 double Get(vtkMark* m, int i) { return 10*i; }

} //... vtkDotMark* m = vtkDotMark::New(); m->SetParameter("size", MySize()); </source>

• Override virtual methods in mark

<source lang="cpp"> class vtkDotMark : public vtkMark { protected:

 virtual double GetSize(int i) { return 10; }

}

class MyMark : public vtkDotMark { protected:

 double GetSize(int i) { return 10*i; }

} //... MyMark* m = MyMark::New(); </source>

• Inherit from parent mark

<source lang="cpp"> vtkDotMark* parent = vtkDotMark::New(); parent->SetParameter("size", 10); vtkDotMark* child = vtkDotMark::New(); parent->Add(child); // Child has size 10 </source>

Parameter Storage and Access

• Named member variables

<source lang="cpp"> class vtkDotMark { public:

 ParamType GetSize() { return this->Size; }
 void SetSize(ParamType p) { this->Size = p; }

private:

 ParamType Size;

} </source>

• Named member variables with import/export to name/value map

<source lang="cpp"> class vtkMark { public:

 ParamType GetParameter(string key)
 { this->ExportSettings()->GetParameter(key); }
 void SetParameter(string key, ParamType p)
 { this->ImportSettings(this->ExportSettings()->SetParameter(key, p)); }
 virtual void ImportSettings(vtkSettings* s) { }
 virtual vtkSettings* ExportSettings() { return vtkSettings::New(); }

}

class vtkDotMark { public:

 ParamType GetSize() { return this->Size; }
 void SetSize(ParamType p) { this->Size = p; }
 virtual vtkSettings* ExportSettings()
 { return this->Parent->ExportSettings()->SetParameter("size", this->Size); }
 virutal void ImportSettings(vtkSettings* s)
 { this->Size = s->GetParameter("size"); }

private:

 ParamType Size;

} </source>

• Generic name/value map

<source lang="cpp"> class vtkMark { public:

 ParamType GetParameter(string key)
 { return this->Parameters[key].Valid ? this->Parameters[key] : this->Parent->GetParameter(key); }
 void SetParameter(string key, ParamType p)
 { this->Parameters[key] = p; }

private:

 map<string, ParamType> Parameters;

} </source>

• Generic name/value map with setter/getter syntactic sugar for discoverability

<source lang="cpp"> class vtkDotMark { public:

 ParamType GetSize() { return this->GetParameter("size"); }
 void SetSize(ParamType p) { this->SetParameter("size", p); }

} </source>

Other Features

• Declarative API
• Iterator support

Further Details on API

Please see VTK/Charts/API for a discussion about the API. There is also more detail about the VTK/Charts/2DAPI and the VTK/Charts/ChartAPI along with proposed class relationships.

Chart Types

• XY plot
• Scatter
• Bar chart
• Histogram
• Stack chart
• Pie chart
• Parallel axes
• Tree map
• Bubble chart

Existing Applications/Libraries

Below is a summary of different libraries or applications that produce 2D charts and plots. Those listed either provide both screen and publication quality rendering, or just screen rendering.

Optimized for Screen Rendering

• prefuse
• tableau
• Many Eyes
• Google Chart
• Qwt
• QwtPlot3D
• QPlotter
• ggobi
• ZedGraph
• TeeChart
• Iocomp
• Scientific charting control
• ChartDirector
• Dundas
• Visifire
• core-plot
• Protoviz

Multiple Backends (Publication Quality)

• PLPlot
• gnuplot
• matplotlib
• Veusz
• Grace
• GLE