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StippledLine

vtk-examples/Cxx/Rendering/StippledLine

Description

VTK OpenGL2 no longer supports Stippled Lines. This example uses texture mapping to created stippled lines. Two parameters, StipplePattern and StippleRepeat, control the pattern of the stippled lines.

StipplePattern is a 16-bit binary pattern, 1 = pixel on, 0 = pixel off.

StippleRepeat is the stippling repeat factor of a Line, which specifies how many times each bit in the pattern is to be repeated.

It can be tricky to set the proper pattern and repeat, so experiment.

Other languages

See (Python)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

StippledLine.cxx

#include <vtkActor.h>
#include <vtkDoubleArray.h>
#include <vtkImageData.h>
#include <vtkLineSource.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkTexture.h>

#include <iostream>
#include <string>

namespace {
void StippledLine(vtkActor* actor, int LineStipplePattern = 0xFFFF,
                  int LineStippleRepeat = 1);
}

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkLineSource> lines;
  // Create two points, P0 and P1
  double p0[3] = {1.0, 0.0, 0.0};
  double p1[3] = {5.0, 0.0, 0.0};

  lines->SetResolution(11);
  lines->SetPoint1(p0);
  lines->SetPoint2(p1);
  lines->Update();
  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(lines->GetOutputPort());

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetLineWidth(5);
  actor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());

  StippledLine(actor, 0xA1A1, 2);

  vtkNew<vtkRenderer> ren1;
  ren1->SetBackground(colors->GetColor3d("SlateGray").GetData());
  vtkNew<vtkRenderWindow> renWin;
  renWin->SetSize(640, 480);
  renWin->SetWindowName("StippledLine");

  renWin->AddRenderer(ren1);
  vtkSmartPointer<vtkRenderWindowInteractor> iren =
      vtkSmartPointer<vtkRenderWindowInteractor>::New();
  iren->SetRenderWindow(renWin);
  ren1->AddActor(actor);

  renWin->Render();
  iren->Start();

  return EXIT_SUCCESS;
}

namespace {
void StippledLine(vtkActor* actor, int lineStipplePattern,
                  int lineStippleRepeat)
{
  vtkNew<vtkDoubleArray> tcoords;
  vtkNew<vtkImageData> image;
  vtkNew<vtkTexture> texture;

  // Create texture.
  int dimension = 16 * lineStippleRepeat;

  image->SetDimensions(dimension, 1, 1);
  image->AllocateScalars(VTK_UNSIGNED_CHAR, 4);
  image->SetExtent(0, dimension - 1, 0, 0, 0, 0);
  unsigned char* pixel;
  pixel = static_cast<unsigned char*>(image->GetScalarPointer());
  unsigned char on = 255;
  unsigned char off = 0;
  for (int i = 0; i < 16; ++i)
  {
    unsigned int mask = (1 << i);
    unsigned int bit = (lineStipplePattern & mask) >> i;
    unsigned char value = static_cast<unsigned char>(bit);
    if (value == 0)
    {
      for (int j = 0; j < lineStippleRepeat; ++j)
      {
        *pixel = on;
        *(pixel + 1) = on;
        *(pixel + 2) = on;
        *(pixel + 3) = off;
        pixel += 4;
      }
    }
    else
    {
      for (int j = 0; j < lineStippleRepeat; ++j)
      {
        *pixel = on;
        *(pixel + 1) = on;
        *(pixel + 2) = on;
        *(pixel + 3) = on;
        pixel += 4;
      }
    }
  }
  vtkPolyData* polyData =
      dynamic_cast<vtkPolyData*>(actor->GetMapper()->GetInput());

  // Create texture coordnates.
  tcoords->SetNumberOfComponents(1);
  tcoords->SetNumberOfTuples(polyData->GetNumberOfPoints());
  for (int i = 0; i < polyData->GetNumberOfPoints(); ++i)
  {
    double value = static_cast<double>(i) * .5;
    tcoords->SetTypedTuple(i, &value);
  }

  polyData->GetPointData()->SetTCoords(tcoords);
  texture->SetInputData(image);
  texture->InterpolateOff();
  texture->RepeatOn();

  actor->SetTexture(texture);
}
} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(StippledLine)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "StippledLine: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(StippledLine MACOSX_BUNDLE StippledLine.cxx )
  target_link_libraries(StippledLine PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS StippledLine
  MODULES ${VTK_LIBRARIES}
)

Download and Build StippledLine

Click here to download StippledLine and its CMakeLists.txt file. Once the tarball StippledLine.tar has been downloaded and extracted,

cd StippledLine/build

If VTK is installed:

cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

make

and run it:

./StippledLine

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.