[Paraview] Setting color / transparency for polydata

[Rafael Küng]

Hi there

For my bachelor thesis, I'm doing a reader in c++ to read in large 
amount of points and display them (from a solar system simulation output 
in a sqlite db), but i fail at setting transparency for certain points. 
Can anybody please point me to a tutorial or give me a hint? I did look 
around and saw i probably need a mapper or actor, with a lookuptable, 
(at least in vtk only it works like this) but i didn't find an example 
how to convert this to paraview. (witch would be great, because i'm 
totally new to pv and vtk).
How and where do i have to attach the mapper to?
I did get the coloring working, but no clue how to continue from here.

Many Thanks

Rafael Kueng
University of zurich

Here's a draft of my code:

int vtkSQLiteReader::RequestData(vtkInformation*,
	vtkInformationVector**,vtkInformationVector* outputVector)
{
	
	vtkPolyData * out = vtkPolyData::GetData(outputVector);

	if (!this->dataIsRead)
		// only read if it's not been read before
	{
		readSnapshots(); //reads in the coordinates and velocities of particles
		readTracks(); //reads in the tracks of the particles

		this->dataIsRead = true;
	}

	out->SetPoints(this->Position);
	out->SetVerts(this->Cells);
	out->SetLines(this->Tracks);
	out->GetPointData()->AddArray(this->Velocity);

	// update the colors in every update
	generateColors();
	out->GetPointData()->SetScalars(this->colors);
	
	return 1;
}


int vtkSQLiteReader::generateColors()
{
	this->colors = vtkSmartPointer<vtkUnsignedCharArray>::New();
	this->colors->SetName("Colors");
	this->colors->SetNumberOfComponents(3);
	this->colors->SetNumberOfTuples(this->nParticles);

	for (int i = 0; i<this->nParticles;i++)
	{
		// heres some code to choose the color per point..
		red = 255;
		green = 255;
		blue = 255;

		this->colors->InsertTuple3(i,
				red,
				green,
				blue);
	}
	return 1;
}