How to show the vtkUnstructuredGrid grid?

Support
1

I want to use the vtkUnstructuredGrid to show some FEA models,but I meet with some problems.

  1. if I turn on the UseFAxxOn(),the grid may look like this picture.
    image
    image788×474 22.5 KB
  2. when I set FAXXOff ,the grid may like this picture. if I dont rotate the model, the grid may show normaly,but if I rotate the model, the grid line look like this picture
    image

here is the core code:

void show(vtkSmartPointer source){

                //source is the grid data
                vtkSmartPointer<vtkMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();

                vtkSmartPointer<vtkDataSetSurfaceFilter> surfaceFilter = vtkSmartPointer<vtkDataSetSurfaceFilter>::New();
                surfaceFilter->SetInputData(source);
                surfaceFilter->Update();

                mapper->SetInputConnection(surfaceFilter->GetOutputPort());
                mapper->SetResolveCoincidentTopologyToPolygonOffset();
                mapper->Update();

                auto   actor = vtkSmartPointer<vtkActor>::New();
                actor->SetMapper(mapper);

                renderer->SetUseDepthPeeling(true);
                renderer->SetMaximumNumberOfPeels(500);
                renderer->SetOcclusionRatio(0.1);
                renderer->UseFXAAOff();
                //renderer->UseFXAAOn();
                renderer->AddActor(actor);

                renderWindow = renderer->GetRenderWindow();


                renderer->Render();
              
              }
2

Hello,

I suggest you to tune the FXAA options:

#include <vtkFXAAOptions.h>

        (...)
        _renderer->UseFXAAOn();

        // configure the FXAA antialiasing
        vtkSmartPointer<vtkFXAAOptions> fxaaOptions = _renderer->GetFXAAOptions();
        fxaaOptions->SetSubpixelBlendLimit( 1/2.0 );
        //fxaaOptions->SetSubpixelContrastThreshold(1/2.0);
        //fxaaOptions->SetRelativeContrastThreshold(0.125);
        //fxaaOptions->SetHardContrastThreshold(0.045);
        //fxaaOptions->SetSubpixelBlendLimit(0.75);
        //fxaaOptions->SetSubpixelContrastThreshold(0.25);
        //fxaaOptions->SetUseHighQualityEndpoints(true);
        //fxaaOptions->SetEndpointSearchIterations(12);

take care,

PC

3

You can also try the slower MSAA that results in better rendering according to some users.

If you’re using Qt:


    // MSAA aliasing (these must be called BEFORE creating a QVTKOpenGLWidget).
    vtkOpenGLRenderWindow::SetGlobalMaximumNumberOfMultiSamples ( 8 );
    QSurfaceFormat::setDefaultFormat ( QVTKOpenGLNativeWidget::defaultFormat() );

    (...)

    //_vtkwidet points to a QVTKOpenGLNativeWidget
    _vtkwidget->renderWindow()->SetMultiSamples( 4 );
4

thanks for your replay,I try to add this code before creating a QVTKOpenGLWidget;
I use this in Qt5 and the version of vtk is vtk9.2

// MSAA aliasing (these must be called BEFORE creating a QVTKOpenGLWidget).
    vtkOpenGLRenderWindow::SetGlobalMaximumNumberOfMultiSamples ( 8 );
    QSurfaceFormat::setDefaultFormat ( QVTKOpenGLNativeWidget::defaultFormat() );

when use the UseFXAAOn()，the intersection point of grid lines may have shadow，like in the picture.

  _renderer->UseFXAAOn();

        // configure the FXAA antialiasing
        vtkSmartPointer<vtkFXAAOptions> fxaaOptions = _renderer->GetFXAAOptions();
        fxaaOptions->SetSubpixelBlendLimit( 1/2.0 );
        //fxaaOptions->SetSubpixelContrastThreshold(1/2.0);
        //fxaaOptions->SetRelativeContrastThreshold(0.125);
        //fxaaOptions->SetHardContrastThreshold(0.045);
        //fxaaOptions->SetSubpixelBlendLimit(0.75);
        //fxaaOptions->SetSubpixelContrastThreshold(0.25);
        //fxaaOptions->SetUseHighQualityEndpoints(true);
        //fxaaOptions->SetEndpointSearchIterations(12);

image
It still have another problem ,if the grid is too dense,the line look discontinuous.
image

5

Have you tried the other FXAA settings?

6

Pelase, don’t enable FXAA and MSAA at the same time. If you choose MSAA, disable everything related to FXAA.

7

I try this,but not improve