The post shows how to use VTK to display 3D model with shading.
We need to make sure the version of VTK is equal to 9 or bigger than it.
To avoid the faceted appearance, compute points’ normal to support to has shading at triangle vertices.

Demo:

#include <iostream>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkActor.h>
#include <vtkConeSource.h>
#include <vtkSphereSource.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkPolyDataNormals.h>
#include <vtkProperty.h>
#include <vtkCamera.h>
#include <vtkLight.h>
#include <vtkSTLReader.h>

#define vtkSPtr vtkSmartPointer
#define vtkSPtrNew(Var, Type) vtkSPtr<Type> Var = vtkSPtr<Type>::New();

using namespace std;

int main()
{
    vtkSPtrNew( reader, vtkSTLReader );
    reader->SetFileName( "string.stl" );
    reader->Update();

    vtkSPtrNew(polyDataNormals, vtkPolyDataNormals);
    polyDataNormals->SetInputData( reader->GetOutput() );
    polyDataNormals->ComputePointNormalsOn();
    polyDataNormals->ComputeCellNormalsOff();
    polyDataNormals->SetSplitting(false);
    polyDataNormals->Update();

    vtkSPtrNew( mapper, vtkPolyDataMapper );
    mapper->SetInputConnection( polyDataNormals->GetOutputPort() );

    vtkSPtrNew( actor, vtkActor );
    actor->SetMapper( mapper );

#if (VTK_MAJOR_VERSION >= 9)
    // Ambient 环境; diffuse 扩散; specular 镜面; coefficient 系数
    actor->GetProperty()->SetInterpolationToPBR(); // shading interpolation: PBR
    actor->GetProperty()->SetRoughness(0.1);
    actor->GetProperty()->SetMetallic(0.05);
    actor->GetProperty()->SetSpecular(0.5);
#endif

    vtkSPtrNew( renderer, vtkRenderer );
    renderer->AddActor(actor);
    renderer->SetBackground( 0, 0, 0 );

    vtkSPtrNew( renderWindow, vtkRenderWindow );
    renderWindow->AddRenderer( renderer );

    vtkSPtrNew( renderWindowInteractor, vtkRenderWindowInteractor );
    renderWindowInteractor->SetRenderWindow( renderWindow );

    renderer->ResetCamera();
    renderWindow->Render();
    renderWindowInteractor->Start();
    return 0;
}

Output:

The faceted surface of model looks like:

    vtkSPtrNew(polyDataNormals, vtkPolyDataNormals);
    polyDataNormals->SetInputData( reader->GetOutput() );
    polyDataNormals->ComputePointNormalsOff();
    polyDataNormals->ComputeCellNormalsOn();
Categories: VTK

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