Zooming in on the surface results in stripes

Development
1

Zooming in on the surface results in stripes, see the picture, how to solve it

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2

Hello,

Please, post the code showing the entire VTK pipeline.

regards,

PC

3

zoom in any shading surface, SetParallelProjection(1), it will show the stripes

4

That doesn’t happen to me. That’s why the code was asked. Lots of artifacts can happen due to misconfigured objects along the pipeline.

5

If you’re just visualizing a surface mesh, is it possible for you to share the data? Sometimes, the points or cell connectivity could be weird.

6

#include <vtkSmartPointer.h>
#include <vtkPolygon.h>
#include <vtkTriangle.h>
#include <vtkCellArray.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkProperty.h>
#include <vtkTextActor.h>
#include <vtkCamera.h>
#include <vtkInteractorStyleTrackballCamera.h>

#include

int main(int argc, char *argv)
{
vtkSmartPointer points = vtkSmartPointer::New();
points->InsertNextPoint(0.0, 0.0, 0.0);
points->InsertNextPoint(1.0, 0.0, 0.0);
points->InsertNextPoint(1.0, 1.0, 0.0);
points->InsertNextPoint(0.0, 1.0, 0.0);
points->InsertNextPoint(2.0, 0.0, 0.0);

vtkSmartPointer<vtkPolygon> polygon = vtkSmartPointer<vtkPolygon>::New();
polygon->GetPointIds()->SetNumberOfIds(4);
polygon->GetPointIds()->SetId(0, 0);
polygon->GetPointIds()->SetId(1, 1);
polygon->GetPointIds()->SetId(2, 2);
polygon->GetPointIds()->SetId(3, 3);

vtkSmartPointer<vtkTriangle> trianle = vtkSmartPointer<vtkTriangle>::New();
trianle->GetPointIds()->SetId(0, 1);
trianle->GetPointIds()->SetId(1, 2);
trianle->GetPointIds()->SetId(2, 4);

vtkSmartPointer<vtkCellArray> cells = vtkSmartPointer<vtkCellArray>::New();
cells->InsertNextCell(polygon);
cells->InsertNextCell(trianle);

vtkSmartPointer<vtkPolyData> polygonPolyData = vtkSmartPointer<vtkPolyData>::New();
polygonPolyData->SetPoints(points);
polygonPolyData->SetPolys(cells);

vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputData(polygonPolyData);

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

vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
renderer->AddActor(actor);
renderer->SetBackground(0.2, 0.8, 0.5);
renderer->GetActiveCamera()->SetParallelProjection(1);

vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->AddRenderer(renderer);
renderWindow->SetSize(640, 480);
renderWindow->Render();
renderWindow->SetWindowName("PolyDataNew");


vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow(renderWindow);

vtkSmartPointer<vtkInteractorStyleTrackballCamera> style = vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();
renderWindowInteractor->SetInteractorStyle(style);

renderWindow->Render();
renderWindowInteractor->Start();

return EXIT_SUCCESS;

}

7

zoom in，zoom in…, the stripes will be appear.

8

@Paulo_Carvalho @jaswantp

9

It looks like you are running into this issue: https://gitlab.kitware.com/vtk/vtk/-/issues/18423

If you provide or generate normals for your surface, then you shouldn’t see this artifact of unstable fragment derivatives.

1 Like
10

It is important to compute point normals, not just cell normals.
Without the point normals the behavior is bad and the renderer may crash on some systems.
I provided an example here

This lets you compare SetComputePointNormals(true) and SetComputePointNormals(false).
-Matthias