rendering - VTK 无法正确渲染多边形

Question

我有一个 VTK 6.3 程序，我已将其精简为下面的列表。

当我运行它时，渲染的多边形不正确。它应该是一个四边形，侧面还有另一个四边形，而不是这个古怪的东西:

看起来多边形三角测量有误，并且当您旋转多边形时，一个流氓三角形会闪烁。

我相信我的多边形已正确指定:逆时针且非自相交。

我仔细研究了 VTK 代码，希望找到一种改变三角测量方法的方法。 VTKPolygon类包含几种不同的三角测量方法，但尚不清楚是否可以手动设置该方法。

如果有人提出解决此问题的建议，我将非常感激。

正如我所说，我相信该列表接近重现问题的最少量代码。

此外，正如评论中所指出的，此行为在 VTK 8.0 版中已修复。但是，我运行的是 RHEL 7.4，安装 VTK 版本 7 或 8 并不简单。 VTK 似乎需要比 RHEL 7.4 可用的版本更新的 OpenGL 版本。

#include <vtkActor.h>
#include <vtkCellArray.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolygon.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <iostream>

using namespace std;

int main (int argc, char **argv)
{
    struct P { float x, y, z; };
    vector<P> p;
    p.push_back (P {8.0, 3.0, 0.0});
    p.push_back (P {7.0, 5.0, 0.0});
    p.push_back (P {1.0, 3.0, 0.0});
    p.push_back (P {1.0, 2.0, 0.0});
    p.push_back (P {0.0, 3.0, 0.0});
    p.push_back (P {0.0, 1.0, 0.0});
    p.push_back (P {1.0, 1.0, 0.0});
    p.push_back (P {1.0, 0.0, 0.0});

    vtkSmartPointer<vtkPolygon> poly = vtkSmartPointer<vtkPolygon>::New();
    poly->GetPointIds()->SetNumberOfIds(p.size ());

    vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
    vtkSmartPointer<vtkCellArray> polygons = vtkSmartPointer<vtkCellArray>::New();

    for (size_t i = 0; i < p.size (); ++i)
    {
        points->InsertNextPoint (p[i].x, p[i].y, p[i].z);
        poly->GetPointIds()->SetId(i, i);
    }

    polygons->InsertNextCell(poly);
    vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();

    polydata->SetPoints(points);
    polydata->SetPolys(polygons);

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

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

    vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
    renderer->AddActor(buildingActor);

    vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
    renderWindow->AddRenderer(renderer);

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

    return 0;
}

Answer 1

我认为VTK对坐标原点有一些技巧。我采用了你的VTK 8.1.1源代码。我更改了坐标集以获得两个在空间中具有不同方向的三角形

我将修改后的源代码放在下面

#include "vtkAutoInit.h"
#define vtkRenderingCore_AUTOINIT 2(vtkRenderingOpenGL2, vtkInteractionStyle)
#include "stdafx.h"


#include <vtkActor.h>
#include <vtkCellArray.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolygon.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <iostream>

using namespace std;

int main(int argc, char **argv)
{
    struct P { float x, y, z; };
    vector<P> p;

    p.push_back(P{ 8.0, 8.0, 3.0 });
    p.push_back(P{ 8.0, 1.0, 0.0 });
    p.push_back(P{ 1.0, 8.0, 0.0 });
    p.push_back(P{ 1.0, 1.0, 3.0 });
    p.push_back(P{ 8.0, 1.0, 0.0 });


    vtkSmartPointer<vtkPolygon> poly = vtkSmartPointer<vtkPolygon>::New();
    poly->GetPointIds()->SetNumberOfIds(p.size());

    vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
    vtkSmartPointer<vtkCellArray> polygons =vtkSmartPointer<vtkCellArray>::New();

    for (size_t i = 0; i < p.size(); ++i)
    {
        points->InsertNextPoint(p[i].x, p[i].y, p[i].z);
        poly->GetPointIds()->SetId(i, i);
    }

    polygons->InsertNextCell(poly);
    vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();

    polydata->SetPoints(points);
    polydata->SetPolys(polygons);

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

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

    vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
    renderer->AddActor(buildingActor);

    vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();

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

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

    return 0;
}