[vtkusers] Rendering performance

[Gib Bogle]

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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