相信大家对曲线并不陌生，在生活学习中都会接触到。同样，在3D方面，曲线大有用处。

什么是样条曲线

引用百度词条：

所谓样条曲线(Spline Curves)是指给定一组控制点而得到一条曲线，曲线的大致形状由这些点予以控制，一般可分为插值样条和逼近样条两种，插值样条通常用于数字化绘图或动画的设计，逼近样条一般用来构造物体的表面。

因此，要拟合一条曲线，控制点是必不可少的，通常点越多越好，但至少需要3个点，曲线的形状则是由曲线方程控制。

如何拟合插值样条曲线

其实思路比较简单，首先要将控制点插到vtkPoints，然后通过vtkParametricSpline来完成拟合。

下面就是由4个控制点拟合的样条曲线效果：

示例代码

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

int main(int, char *[])

{

double p0[3] = { 1.0, 0.0, 0.0 };

double p1[3] = { 0.0, 1.0, 0.0 };

double p2[3] = { 0.0, 0.0, 1.0 };

double p3[3] = { 1.0, 2.0, 3.0 };

vtkSmartPointer points =

vtkSmartPointer::New();

points->InsertNextPoint(p0);

points->InsertNextPoint(p1);

points->InsertNextPoint(p2);

points->InsertNextPoint(p3);

vtkSmartPointer spline =

vtkSmartPointer::New();

spline->SetPoints(points);

vtkSmartPointer functionSource =

vtkSmartPointer::New();

functionSource->SetParametricFunction(spline);

functionSource->Update();

vtkSmartPointer splineMapper =

vtkSmartPointer::New();

splineMapper->SetInputConnection(functionSource->GetOutputPort());

vtkSmartPointer splineActor =

vtkSmartPointer::New();

splineActor->SetMapper(splineMapper);

vtkSmartPointer sphereSource =

vtkSmartPointer::New();

sphereSource->SetPhiResolution(21);

sphereSource->SetThetaResolution(21);

sphereSource->SetRadius(.1);

vtkSmartPointer splinePointsData =

vtkSmartPointer::New();

splinePointsData->SetPoints(points);

vtkSmartPointer splinePointsMapper =

vtkSmartPointer::New();

splinePointsMapper->SetInputData(splinePointsData);

splinePointsMapper->SetSourceConnection(sphereSource->GetOutputPort());

vtkSmartPointer pointsActor =

vtkSmartPointer::New();

pointsActor->SetMapper(splinePointsMapper);

pointsActor->GetProperty()->SetColor(1, 0, 0);

vtkSmartPointer renderer =

vtkSmartPointer::New();

vtkSmartPointer renderWindow =

vtkSmartPointer::New();

renderWindow->SetSize(600, 600);

renderWindow->AddRenderer(renderer);

vtkSmartPointer renderWindowInteractor =

vtkSmartPointer::New();

renderWindowInteractor->SetRenderWindow(renderWindow);

renderer->AddActor(splineActor);

renderer->AddActor(pointsActor);

renderWindow->Render();

renderWindowInteractor->Start();

return EXIT_SUCCESS;

}