[vtkusers] Rendering performance

[Gib Bogle]

Seb, if this is what you are referring to:
http://www.itk.org/Wiki/VTK/Java_Code_Samples
it might require skills a bit beyond my rather primitive level of C++  
expertise.

Gib

Quoting Sebastien Jourdain <sebastien.jourdain at kitware.com>:

> You can use a single actor, you will need to have a programable source
> that update the output dataset that has the location of each center of
> the square.
>
> Pipeline: Actor(Mapper(Glyph(CustomSource, Square)))
>
> To change the position of a square, you can have something like that...
>
> customSource.SetSquarePosition( suquareId, xyz )
>
> Seb
>
> PS: I think I wrote a sample code in Java for programmable source on  
> the wiki...
>
>
> On Wed, Nov 24, 2010 at 1:41 PM, Gib  Bogle <g.bogle at auckland.ac.nz> wrote:
>> Hi Seb,
>>
>> Although I referred to a simplified case in which the squares don't change,
>> in general I need to allow for their movement.  Therefore I don't think it
>> will be possible for me to use a single actor.  If I'm wrong, could you
>> please provide a bit more  detail?
>>
>> Thanks
>> Gib
>>
>> Quoting Sebastien Jourdain <sebastien.jourdain at kitware.com>:
>>
>>> Hi Gib,
>>>
>>> My first question will be. Are you using one actor for each of your
>>> 10000 flat squares ?
>>> If so, the performance limitation may come from the number of actors
>>> involved. One solution to that is to create only one dataset with all
>>> the squares that has only one mapper and actor. To do so, you can
>>> build it by hand or simply use the Glyph filter with your square as a
>>> glyph and another dataset that has the location of those squares.
>>>
>>> Seb
>>>
>>>
>>> On Wed, Nov 24, 2010 at 12:44 AM, Gib Bogle <g.bogle at auckland.ac.nz>
>>> wrote:
>>>>
>>>> I asked about this before, but didn't attract any responses.  I have a
>>>> better understanding of the issue now, so perhaps my questions will make
>>>> more sense.
>>>>
>>>> At regular intervals as my simulation program executes, I am rendering a
>>>> scene that contains mainly about 1000 small spheres (which move) and
>>>> about
>>>> 10000 flat squares (which do not move).  I have discovered that the
>>>> surprising slowness of the the rendering is caused by the squares, even
>>>> though the spheres have ThetaResolution and PhiResolution both equal to
>>>> 12,
>>>> which I guess means 144 faces per sphere, i.e. a total of 144,000 faces.
>>>>  By
>>>> my calculations rendering the scene 288 times with spheres alone takes
>>>> about
>>>> 4 sec, with the squares alone takes about 20 sec, and with both spheres
>>>> and
>>>> squares about 24 sec.  That is, 10,000 squares take 5 times as long as
>>>> 1000
>>>> spheres with 144,000 faces.
>>>>
>>>> Apparently there's something very inefficient about the way I am
>>>> rendering
>>>> the squares.  Here is the code for tileMapper (which makes squares):
>>>>
>>>> // Create the square
>>>> // Setup points to draw a unit square in the XY plane, at y=0
>>>> vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
>>>> vtkSmartPointer<vtkCellArray> vertices =
>>>> vtkSmartPointer<vtkCellArray>::New();
>>>> points->InsertNextPoint(-0.5, 0.0, -0.5);
>>>> points->InsertNextPoint( 0.5, 0.0, -0.5);
>>>> points->InsertNextPoint( 0.5, 0.0,  0.5);
>>>> points->InsertNextPoint(-0.5, 0.0,  0.5);
>>>>
>>>> vtkSmartPointer<vtkPolygon> polygon = vtkSmartPointer<vtkPolygon>::New();
>>>> polygon->GetPointIds()->SetNumberOfIds(4); //make a quad
>>>> polygon->GetPointIds()->SetId(0, 0);
>>>> polygon->GetPointIds()->SetId(1, 1);
>>>> polygon->GetPointIds()->SetId(2, 2);
>>>> polygon->GetPointIds()->SetId(3, 3);
>>>>
>>>> //Add the polygon to a list of polygons
>>>> vtkSmartPointer<vtkCellArray> polygons =
>>>> vtkSmartPointer<vtkCellArray>::New();
>>>> polygons->InsertNextCell(polygon);
>>>>
>>>> //Create a PolyData
>>>> vtkSmartPointer<vtkPolyData> polygonPolyData =
>>>> vtkSmartPointer<vtkPolyData>::New();
>>>> polygonPolyData->SetPoints(points);
>>>> polygonPolyData->SetPolys(polygons);
>>>>
>>>> //Create a mapper and actor
>>>> tileMapper = vtkPolyDataMapper::New();
>>>> tileMapper->SetInput(polygonPolyData);
>>>> tileMapper->ScalarVisibilityOff();
>>>>
>>>> The square actors are made like this:
>>>>
>>>> actor = vtkActor::New();
>>>> actor->SetMapper(tileMapper);
>>>> actor->GetProperty()->SetColor(boneColor);
>>>> actor->GetProperty()->SetAmbient(0.5);
>>>> actor->GetProperty()->SetDiffuse(0.2);
>>>> actor->GetProperty()->SetSpecular(0.5);
>>>> actor->SetPosition(pos);
>>>> ren->AddActor(actor);
>>>>
>>>> then not touched again (in the simulations I report times for.)
>>>>
>>>> I'd be very grateful if someone could give me a clue as to what I'm doing
>>>> wrong to make the rendering so slow.
>>>>
>>>> Thanks
>>>> Gib
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>>>
>>
>>
>>
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