[vtkusers] Vector arrows form a solid patch. How to rectify??

[Rakesh Patil]

 Hi David,Thanks for your precious information. It will be grateful of you if you guide me in implementing this feature. How do I hook into the Renderer's StartEvent.?? Where my callback command should be implemented?? Thanks Original message From:David Gobbi< david.gobbi at gmail.com >Date: 28 Jan 10 23:04:33Subject:Re: [vtkusers] Vector arrows form a solid patch. How to rectify??To: Rakesh Patil Hi Rakesh,I've had to deal with this same issue in my own software.A goodsolution is to use observers.Usually, I hook into the Renderer's StartEvent.Inside myCommandCallback, I check the renderer to see how much I need to scalethe actor in order make it always be the same number of pixels across:double vtkSurfaceCursor::ComputeScale(const double position[3],vtkRenderer *renderer){// Find the cursor scale factor such that 1 data unit length// equals 1 screen pixel at the cursor's distance from the camera.// Start by computing the height of the window at the cursor position.double worldH
 eight = 1.0;vtkCamera *camera = renderer>GetActiveCamera();if (camera>GetParallelProjection()){worldHeight = 2*camera>GetParallelScale();}else{double cameraPosition[3];camera>GetPosition(cameraPosition);worldHeight = 2*(sqrt(vtkMath::Distance2BetweenPoints(position,cameraPosition)) * tan(0.5*camera>GetViewAngle()/57.296));}// Compare world height to window height.int windowHeight = renderer>GetSize()[1];double scale = 1.0;if (windowHeight > 0){scale = worldHeight/windowHeight;}return scale;}I hope this is the sort of thing that you were looking for.  David GOn Thu, Jan 28, 2010 at 9:53 AM, Rakesh Patilwrote:>> i guess, the way i explained the problem was not correct.. here it goes,>> for a large area, if i draw vecot of actual size, it will be visible as a> small dot. So i need to scale and make it> large enough that it is visible properly.. And as i zoom in, and go closer> to them, they must slowly,> shrink to their actual size...>> As kaarthik said, i think i need to write
  my own actor . But how to do it,> am not able to understand..> can anyone guide me..??>> Thanks> Regards>>  Original message > From:David Doria< daviddoria+vtk at gmail.com >> Date: 27 Jan 10 19:54:04> Subject: Re: [vtkusers] Vector arrows form a solid patch. How to rectify??> To: rakeshthp at in.com>> On Wed, Jan 27, 2010 at 8:56 AM, Rakesh Patil wrote:>> Hello,>>>> I dont know mush about wrapping the code. It would be nice if anyone helps>> me out. Here is my code to display vectors>>>> unsigned int numpts = x.size();>>>> vtkPoints *pts = vtkPoints::New();>> pts>SetNumberOfPoints(numpts);>>>> vtkDoubleArray *vecArr = vtkDoubleArray::New();>> vecArr>SetNumberOfComponents(3);>> vecArr>SetNumberOfTuples(numpts);>>>> for( unsigned int i=0; i < numpts; i++)>> {>> pts>InsertPoint(i, x(i), y(i), 0);>> vecArr>InsertTuple2(i, velu(i), velv(i));>> }>>>> unsigned int numcells = elem.rows(); // elem is a matrix that contains>> the>> index of nodes of elements in the mesh>>>> vtkCellArray *
 cellA = vtlCellArray::New();>> cellA>SetNumberOfCells(numcells);>>>> for (unsigned int i=0; i < numcells; i++)>> {>> cellA>InsertNextCell(3);>> cellA>InsertCellPoint( elem(i, 0) );>> cellA>InsertCellPoint( elem(i, 1) );>> cellA>InsertCellPoint( elem(i, 2) );>> }>>>> vtkUnstructuredGrid *uGrid = vtkUnstructuredGrid::New();>> uGrid>Allocate(numcells, numcells);>> uGrid>SetCells( VTKTRIANGLE, cellA);>> uGrid>SetPoints(pts);>> uGrid>GetPointData()>SetVector(vecArr);>>>> vtkGlyph2D *glyph = vtkGlyph2D::New();>> glyph>SetInput(uGrid);>> glyph>SetColorModeToColorByVector();>> glyph>OrientOn();>> glyph>SetScaleFactor(1);>>>> vtkGlyphSource2D *glyphSource = vtkGlyphSource2D::New();>> glyphSource>FilledOff();>> glyphSource>SetGlyphTypeToArrow();>>>> glyph>SetInputConnection(1, glyphSource>GetOutputPort());>>>> vtkPolyDataMapper *gMapper = vtkPolyDataMapper::New();>> gMapper>SetInput( glyph>GetOutput());>> gMapper>ScalarVisibilityOn();>> gMapper>SetScalarRange(uGrid>GetScalarRange());>
 >>> vtkActor *gactor = vtkActor::New();< br>> gactor>SetMapper(gMapper);>>>> pRenderer>AddActor(gactor);>>>> pRenderer>Rese tCamera();>>>> Do i need to derive a class from vtkActor and override>> RenderOpaqueGeometry>> code..?? If so, then how do i scale the glyphs..?? and which part will>> this>> code come into picture. Am not that much expert in C++ but can manage with>> a>> guidance.>>>> Thanks>>>> Regards>>>>  Original message >> From:Karthik Krishnan< karthik.krishnan at kitware.com >>> Date: 25 Jan 10 17:08:12>> Subject: Re: [vtkusers] Vector arrows form a solid patch. How to rectify??>> To: Rakesh Patil>>>> You'll have to write your own actor wrapping around your existing code>> and overriding RenderOpaqueGeometry. Its not hard. See several actors>> in VTK/Rendering that scale their font size based on the size of the>> viewport etc. Yo u may have to do something similar scaling your glyphs>> based on the parallel scale / view angle.>>>> On Sat, Jan 23, 2010 at 12:49 PM, 
 Rakesh Patil wrote:>>> hello,>>>>>> When i display a vector plot using vtk, it is shown very small like a>>> dot.>>> And when i zoom into it, it gets more visible and big. But, i want it in>>> such a way, that when i display it, at the initial stage itself, the>>> vectors>>> must be big enough that can be seen. And when we zoom into it, then the>>> arrow size must proportionately become small. I Used setscalefactor for>>> glyph object and got the arrow size increased.>>>>>> But where the data is very dense, there a solid patch is formed due to>>> which>>> i cannot make out whats the length of the arrow. So as we zoom in, the>>> arrow>>> size must be reduced so that at the denser location, i ca n differentiate>>> among two vectors. How can i do this..??>>>>>> Thanks in advance>>>>>> Regards>>> Rakesh>>>>>> Get Yourself a cool, short @in.com Email ID now!>>>  >>> Powered by www.kitware.com>>>>>> Visit other Kitware opensource projects at>>> http://www.kitware.com/opensource/op
 ensource.html>>>>>> Please keep messages ontopic and check the VTK FAQ at:>>> http://www.vtk.org/Wiki/VTKFAQ>>>>>> Follow this link to subscribe/unsubscribe:>>> http://www.vtk.org/mailman/listinfo/vtkusers>>>> >> Karthik Krishnan>> This is only a very partial answer, but you can scale an arrow using> the vtkTransformFilter like this:>> http://www.vtk.org/Wiki/VTK/Examples/TransformFilter>> Thanks,>> David> > Powered by www.kitware.com>> Visit other Kitware opensource projects at> http://www.kitware.com/opensource/opensource.html>> Please keep messages ontopic and check the VTK FAQ at:> http://www.vtk.org/Wiki/VTKFAQ>> Follow this link to subscribe/unsubscribe:> http://www.vtk.org/mailman/listinfo/vtkusers> < /blockquote>>> Get Yourself a cool, short @in.com Email ID now!>> > Powered by www.kitware.com>> Visit other Kitware opensource projects at> http://www.kitware.com/opensource/opensource.html>> Please keep messages ontopic and check the VTK FAQ at:> http://www.vtk.org/Wik
 i/VTKFAQ>> Follow this link to subscribe/unsubscribe:> http://www.vtk.org/mailman/listinfo/vtkusers>> 
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