VTK交互之拾取选择拾取示例演示

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我是靠谱客的博主瘦瘦山水，这篇文章主要介绍VTK交互之拾取选择拾取示例演示，现在分享给大家，希望可以做个参考。

选择拾取

　　选择拾取是人机交互过程的一个重要功能。VTK中定义了多个拾取功能的类，所有拾取类都继承自vtkAbstractPicker类，继承关系如下:

这里写图片描述

1. vtkAbstractPicker

　　该类是一个抽象基类，为它的具体的子类定义了最基本的API，最基本的功能是返回拾取位置的x-y-z 世界坐标系统的坐标值(pick自身是在屏幕坐标中进行定义的) 。
　　类定义了一个纯虚函数Pick()，它的作用是给定一个选择点(屏幕坐标系统里的，以像素为单位)以及一个Renderer，然后通过调用GetPickPosition()方法，生成世界坐标系统的坐标值。
Pick()函数的原型如下：

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virtual int Pick (double selectionX, double selectionY, double selectionZ, vtkRenderer *renderer)

　　　通常都把selectionZ设为0，与Renderer相关联的actor就是拾取的对象范围。在拾取过程中vtkPicker会触发一些事件：1、StartPickEvent, 2、PickEvent, 3、EndPickEvent。当something被拾取的时候，并且在所有的picking申请者已经通过测试,1/2/3事件就会在picking之前调用。注意：在pick的过程中，vtkProp的PickEvent事件会在vtkPicker的PickEvent之前被调用。　
　　 vtkAbstractPicker以及它的子类都不能拾取”拒绝拾取”的Prop(也就是该Prop通过调用自身的PickableOff()方法)和完全透明的Prop(即prop->GetProperty()->SetOpacity(0))。
　　Picker可以分为两类，分别是用几何方法拾取(典型的例子是光线投射)和基于硬件拾取。几何方法拾取能获取的信息较多同时也较慢，而基于硬件的拾取拾取速度快，但返回的信息最少。几何方法拾取主要的类有：vtkPicker, vtkCellPicker和vtkPointPicker。基于硬件拾取的类有：vtkWorldPointPicker和vtkPropPicker。vtkAbstractPicker有两个直接子类：vtkWorldPointPicker和vtkAbstractPropPicker。

2. vtkWorldPointPicker

　　vtkWorldPointPicker是基于硬件的拾取，它返回与屏幕坐标(x, y, z)相对应的世界坐标点。这个类不能拾取Actor和/或Mapper，它只是简单地确定世界坐标上的坐标值。这个类不调用PickMethod()事件，只能调用StartPickEvent()和EndPickMethod()两个事件。

3. vtkPropPicker

　　 vtkPropPicker是基于图形硬件拾取一个Actor/Prop实例，速度比vtkCellPicker/vtkPointPicker快。这个类在世界坐标系统中判定Actor/Prop和拾取位置，对于点和单元的ID则不作判定。

4. vtkPicker

　　vtkPicker用于拾取vtkProp3D实例，它通过发射一条光线到图形窗口中，并与Actor的线框(Bounding box)相交，光线是从窗口坐标系统中拾取的一点到相机所在的位置的连线。因为光线可能会与多个Actor的线框相交，所以可能会返回多个vtkProp3D的实例。vtkPicker返回的是与光线相交的Prop实例的一个列表、世界坐标系统中的拾取坐标以及最靠近相机的Prop和Mapper实例。所谓的最靠近相机，是指该Prop线框中心点在光线上的投影最靠近相机的那个Prop实例。vtkPicker速度相对较快，可用于快速拾取几何对象。但如果想返回拾取的点或者单元的话，得用它的子类vtkCellPicker和vtkPointPicker vtkPicker里其中有一个方法：virtual void SetTolerance(double)—-是设置容差。

5. vtkPointPicker

　　vtkPointPicker是vtkPicker的子类，它返回选择点的ID以及坐标。它也是通过发射光线与Actor相交而拾取对象的，除了返回坐标值，Actor和Mapper，它也返回在指定容差内沿着光线，最靠近光线的那个点的ID。vtkPointPicker::GetPointId()可以获取点的ID号。
　　vtkPointPicker不能单一拾取，其速度比vtkPicker慢，但比vtkCellPicker要快。

6. vtkCellPicker

　　vtkCellPicker是vtkPicker的子类，它返回选择单元的ID以及坐标。它也是通过发射光线与Actor相交而拾取对象的，除了返回坐标值，Actor和Mapper，它也返回在指定容差内沿着光线，最靠近光线的那个单元的ID。vtkPointPicker::GetCellId()可以获取单元的ID号。vtkCellPicker可以单一拾取，其速度是所有Picker中最慢的，当然，提供的信息也是最丰富的。

示例演示

CMakeLists.txt文件代码如下：

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CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
PROJECT(PropPickerExample)
FIND_PACKAGE(VTK REQUIRED)
INCLUDE(${VTK_USE_FILE})
ADD_EXECUTABLE(PropPickerExample
PropPickerExample.cpp)
TARGET_LINK_LIBRARIES(PropPickerExample
${VTK_LIBRARIES})

PropPickerExample.cpp文件代码如下：

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#include <vtkSmartPointer.h>
#include <vtkMath.h>
#include <vtkActor.h>
#include <vtkProperty.h>
#include <vtkSphereSource.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkObjectFactory.h>
#include <vtkSphereSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkPropPicker.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
// Handle mouse events
class PropPickerInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
static PropPickerInteractorStyle* New();
vtkTypeMacro(PropPickerInteractorStyle, vtkInteractorStyleTrackballCamera);
PropPickerInteractorStyle()
{
LastPickedActor = NULL;
LastPickedProperty = vtkProperty::New();
}
virtual ~PropPickerInteractorStyle()
{
LastPickedProperty->Delete();
}
virtual void OnLeftButtonDown()
{
int* clickPos = this->GetInteractor()->GetEventPosition();
// Pick from this location.
vtkSmartPointer<vtkPropPicker>
picker =
vtkSmartPointer<vtkPropPicker>::New();
picker->Pick(clickPos[0], clickPos[1], 0, this->GetDefaultRenderer());
double* pos = picker->GetPickPosition();
// If we picked something before, reset its property
if (this->LastPickedActor)
{
this->LastPickedActor->GetProperty()->DeepCopy(this->LastPickedProperty);
}
this->LastPickedActor = picker->GetActor();
if (this->LastPickedActor)
{
// Save the property of the picked actor so that we can restore it next time
this->LastPickedProperty->DeepCopy(this->LastPickedActor->GetProperty());
// Highlight the picked actor by changing its properties
this->LastPickedActor->GetProperty()->SetColor(1.0, 0.0, 0.0);
this->LastPickedActor->GetProperty()->SetDiffuse(1.0);
this->LastPickedActor->GetProperty()->SetSpecular(0.0);
}
// Forward events
vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
}
private:
vtkActor
*LastPickedActor;
vtkProperty *LastPickedProperty;
};
vtkStandardNewMacro(PropPickerInteractorStyle);
int main(int argc, char *argv[])
{
int numberOfSpheres = 10;
if (argc > 1)
{
numberOfSpheres = atoi(argv[1]);
}
// A renderer and render window
vtkSmartPointer<vtkRenderer> renderer =
vtkSmartPointer<vtkRenderer>::New();
vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->Render();
renderWindow->SetWindowName("PropPicker");
renderWindow->AddRenderer ( renderer );
// An interactor
vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow ( renderWindow );
// Set the custom type to use for interaction.
vtkSmartPointer<PropPickerInteractorStyle> style =
vtkSmartPointer<PropPickerInteractorStyle>::New();
style->SetDefaultRenderer(renderer);
renderWindowInteractor->SetInteractorStyle( style );
for (int i = 0; i < numberOfSpheres; ++i)
{
vtkSmartPointer<vtkSphereSource> source =
vtkSmartPointer<vtkSphereSource>::New();
double x, y, z, radius;
x = vtkMath::Random(-5,5);
y = vtkMath::Random(-5,5);
z = vtkMath::Random(-5,5);
radius = vtkMath::Random(.5, 1.0);
source->SetRadius(radius);
source->SetCenter(x, y, z);
source->SetPhiResolution(11);
source->SetThetaResolution(21);
vtkSmartPointer<vtkPolyDataMapper> mapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputConnection ( source->GetOutputPort());
vtkSmartPointer<vtkActor> actor =
vtkSmartPointer<vtkActor>::New();
actor->SetMapper ( mapper );
double r, g, b;
r = vtkMath::Random(.4, 1.0);
g = vtkMath::Random(.4, 1.0);
b = vtkMath::Random(.4, 1.0);
actor->GetProperty()->SetDiffuseColor(r, g, b);
actor->GetProperty()->SetDiffuse(.8);
actor->GetProperty()->SetSpecular(.5);
actor->GetProperty()->SetSpecularColor(1.0,1.0,1.0);
actor->GetProperty()->SetSpecularPower(30.0);
renderer->AddActor ( actor );
}
renderer->SetBackground ( 1.0, 1.0, 1.0 );
// Render and interact
renderWindow->Render();
renderWindowInteractor->Initialize();
renderWindowInteractor->Start();
return EXIT_SUCCESS;
}

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#include <vtkSmartPointer.h>
#include <vtkMath.h>
#include <vtkActor.h>
#include <vtkProperty.h>
#include <vtkSphereSource.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkObjectFactory.h>
#include <vtkSphereSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkPropPicker.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
// Handle mouse events
class PropPickerInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
static PropPickerInteractorStyle* New();
vtkTypeMacro(PropPickerInteractorStyle, vtkInteractorStyleTrackballCamera);
PropPickerInteractorStyle()
{
LastPickedActor = NULL;
LastPickedProperty = vtkProperty::New();
}
virtual ~PropPickerInteractorStyle()
{
LastPickedProperty->Delete();
}
virtual void OnLeftButtonDown()
{
int* clickPos = this->GetInteractor()->GetEventPosition();
// Pick from this location.
vtkSmartPointer<vtkPropPicker>
picker =
vtkSmartPointer<vtkPropPicker>::New();
picker->Pick(clickPos[0], clickPos[1], 0, this->GetDefaultRenderer());
double* pos = picker->GetPickPosition();
// If we picked something before, reset its property
if (this->LastPickedActor)
{
this->LastPickedActor->GetProperty()->DeepCopy(this->LastPickedProperty);
}
this->LastPickedActor = picker->GetActor();
if (this->LastPickedActor)
{
// Save the property of the picked actor so that we can restore it next time
this->LastPickedProperty->DeepCopy(this->LastPickedActor->GetProperty());
// Highlight the picked actor by changing its properties
this->LastPickedActor->GetProperty()->SetColor(1.0, 0.0, 0.0);
this->LastPickedActor->GetProperty()->SetDiffuse(1.0);
this->LastPickedActor->GetProperty()->SetSpecular(0.0);
}
// Forward events
vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
}
private:
vtkActor
*LastPickedActor;
vtkProperty *LastPickedProperty;
};
vtkStandardNewMacro(PropPickerInteractorStyle);
int main(int argc, char *argv[])
{
int numberOfSpheres = 10;
if (argc > 1)
{
numberOfSpheres = atoi(argv[1]);
}
// A renderer and render window
vtkSmartPointer<vtkRenderer> renderer =
vtkSmartPointer<vtkRenderer>::New();
vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->Render();
renderWindow->SetWindowName("PropPicker");
renderWindow->AddRenderer ( renderer );
// An interactor
vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow ( renderWindow );
// Set the custom type to use for interaction.
vtkSmartPointer<PropPickerInteractorStyle> style =
vtkSmartPointer<PropPickerInteractorStyle>::New();
style->SetDefaultRenderer(renderer);
renderWindowInteractor->SetInteractorStyle( style );
for (int i = 0; i < numberOfSpheres; ++i)
{
vtkSmartPointer<vtkSphereSource> source =
vtkSmartPointer<vtkSphereSource>::New();
double x, y, z, radius;
x = vtkMath::Random(-5,5);
y = vtkMath::Random(-5,5);
z = vtkMath::Random(-5,5);
radius = vtkMath::Random(.5, 1.0);
source->SetRadius(radius);
source->SetCenter(x, y, z);
source->SetPhiResolution(11);
source->SetThetaResolution(21);
vtkSmartPointer<vtkPolyDataMapper> mapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputConnection ( source->GetOutputPort());
vtkSmartPointer<vtkActor> actor =
vtkSmartPointer<vtkActor>::New();
actor->SetMapper ( mapper );
double r, g, b;
r = vtkMath::Random(.4, 1.0);
g = vtkMath::Random(.4, 1.0);
b = vtkMath::Random(.4, 1.0);
actor->GetProperty()->SetDiffuseColor(r, g, b);
actor->GetProperty()->SetDiffuse(.8);
actor->GetProperty()->SetSpecular(.5);
actor->GetProperty()->SetSpecularColor(1.0,1.0,1.0);
actor->GetProperty()->SetSpecularPower(30.0);
renderer->AddActor ( actor );
}
renderer->SetBackground ( 1.0, 1.0, 1.0 );
// Render and interact
renderWindow->Render();
renderWindowInteractor->Initialize();
renderWindowInteractor->Start();
return EXIT_SUCCESS;
}