【VTK-Rendering::Annotation】第一期 vtkCaptionActor2D

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前言

本文分享vtkCaptionActor2D源码解析，希望对各位小伙伴有所帮助！

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前言

1. vtkCaptionActor2D概述

2. 重要参数

2.1 定义标注文本

2.2 设置标注附着点

2.3 设置是否启用边框

2.4 设置是否启用标注到附着点的引导线

2.5 指定2D或3D箭头

2.6 设置文本与包围盒的距离

2.7 设置文本属性

2.8 设置箭头是否在Edge上附着

3. 原理解析

3.1 vtkBorderRepresentation原理解析

结论：

1. vtkCaptionActor2D概述

vtkCaptionActor2D是一个2DActor和3DActor混合的对象，用于将文本与场景中的点(AttachmentPoint)相关联。可以使用矩形边框和将标题连接到附着点的引线来绘制标题。可选地，可以在leader的端点处对其进行符号化，以创建箭头或其他指示符。

使用vtkCaptionActor2D时，必须指定Position和Position2两个点。Position和Position2定义标题的大小，AttachmentPoint定义标题所关联的点。还必须定义标题文本、是否希望在标题周围设置边框，以及是否希望在标题到附件点之间设置一个引线。

文本的属性通过关联的vtkTextProperty进行设置。引线可以设置为2D或3D。（2D绘制在底层几何上，3D三维引线可能被几何遮挡。）

2. 重要参数

2.1 定义标注文本

  //@{/*** Define the text to be placed in the caption. The text can be multiple* lines (separated by "\n").* 定义标注的文本，文本可以多行（通过"\n"进行分隔）*/virtual void SetCaption(const char* caption);virtual char* GetCaption();//@}

2.2 设置标注附着点

  //@{/*** Set/Get the attachment point for the caption. By default, the attachment* point is defined in world coordinates, but this can be changed using* vtkCoordinate methods.* 设置标注的附着点，默认为世界坐标系。可以通过vtkCoordinate的方法进行更改*/vtkWorldCoordinateMacro(AttachmentPoint);//@}

2.3 设置是否启用边框

  //@{/*** Enable/disable the placement of a border around the text.* 可用/不可用文本外的包围框*/vtkSetMacro(Border, vtkTypeBool);vtkGetMacro(Border, vtkTypeBool);vtkBooleanMacro(Border, vtkTypeBool);//@}

2.4 设置是否启用标注到附着点的引导线

  //@{/*** Enable/disable drawing a "line" from the caption to the* attachment point.* 可用/不可用 标注到附着点的线*/vtkSetMacro(Leader, vtkTypeBool);vtkGetMacro(Leader, vtkTypeBool);vtkBooleanMacro(Leader, vtkTypeBool);//@}

2.5 指定2D或3D箭头

  //@{/*** Indicate whether the leader is 2D (no hidden line) or 3D (z-buffered).* 指定箭头为2D或3D*/vtkSetMacro(ThreeDimensionalLeader, vtkTypeBool);vtkGetMacro(ThreeDimensionalLeader, vtkTypeBool);vtkBooleanMacro(ThreeDimensionalLeader, vtkTypeBool);//@}//@{/*** Specify a glyph to be used as the leader "head". This could be something* like an arrow or sphere. If not specified, no glyph is drawn. Note that* the glyph is assumed to be aligned along the x-axis and is rotated about* the origin. SetLeaderGlyphData() directly uses the polydata without* setting a pipeline connection. SetLeaderGlyphConnection() sets up a* pipeline connection and causes an update to the input during render.* 设置箭头的头部输入数据*/virtual void SetLeaderGlyphData(vtkPolyData*);virtual void SetLeaderGlyphConnection(vtkAlgorithmOutput*);virtual vtkPolyData* GetLeaderGlyph();//@}//@{/*** Specify the relative size of the leader head. This is expressed as a* fraction of the size (diagonal length) of the renderer. The leader* head is automatically scaled so that window resize, zooming or other* camera motion results in proportional changes in size to the leader* glyph.* 设置箭头符号的大小*/vtkSetClampMacro(LeaderGlyphSize, double, 0.0, 0.1);vtkGetMacro(LeaderGlyphSize, double);//@}//@{/*** Specify the maximum size of the leader head (if any) in pixels. This* is used in conjunction with LeaderGlyphSize to cap the maximum size of* the LeaderGlyph.* 像素上设置箭头符号的最大像素值*/vtkSetClampMacro(MaximumLeaderGlyphSize, int, 1, 1000);vtkGetMacro(MaximumLeaderGlyphSize, int);//@}

2.6 设置文本与包围盒的距离

  //@{/*** Set/Get the padding between the caption and the border. The value* is specified in pixels.* 设置/获取标注文本和包围框之间的距离*/vtkSetClampMacro(Padding, int, 0, 50);vtkGetMacro(Padding, int);//@}//@{/*** Get the text actor used by the caption. This is useful if you want to control* justification and other characteristics of the text actor.* 获取文本Actor对象*/vtkGetObjectMacro(TextActor, vtkTextActor);//@}

2.7 设置文本属性

  //@{/*** Set/Get the text property.* 设置文本的属性*/virtual void SetCaptionTextProperty(vtkTextProperty* p);vtkGetObjectMacro(CaptionTextProperty, vtkTextProperty);//@}

2.8 设置箭头是否在Edge上附着

  //@{/*** Enable/disable whether to attach the arrow only to the edge,* NOT the vertices of the caption border.* 箭头在包围框上的附着点；若为On时，表示附着点考虑包围框四个边的中点；否则不考虑*/vtkSetMacro(AttachEdgeOnly, vtkTypeBool);vtkGetMacro(AttachEdgeOnly, vtkTypeBool);vtkBooleanMacro(AttachEdgeOnly, vtkTypeBool);//@}

3. 原理解析

3.1 vtkBorderRepresentation原理解析

定义一个矩形，左下角点为（0.，0.，0.），右上角点为（1.，1.，0.）。

定义由这四个点组成的矩形边界的PolyData数据

  // Create the geometry in canonical coordinatesthis->BWPoints = vtkPoints::New();this->BWPoints->SetDataTypeToDouble();this->BWPoints->SetNumberOfPoints(4);this->BWPoints->SetPoint(0, 0.0, 0.0, 0.0); // may be updated by the subclassthis->BWPoints->SetPoint(1, 1.0, 0.0, 0.0);this->BWPoints->SetPoint(2, 1.0, 1.0, 0.0);this->BWPoints->SetPoint(3, 0.0, 1.0, 0.0);vtkCellArray* outline = vtkCellArray::New();outline->InsertNextCell(5);outline->InsertCellPoint(0);outline->InsertCellPoint(1);outline->InsertCellPoint(2);outline->InsertCellPoint(3);outline->InsertCellPoint(0);this->BWPolyData = vtkPolyData::New();this->BWPolyData->SetPoints(this->BWPoints);this->BWPolyData->SetLines(outline);outline->Delete();

给PolyData数据添加Transform变换，并将其映射为actor2D 数据。

  this->BWTransform = vtkTransform::New();this->BWTransformFilter = vtkTransformPolyDataFilter::New();this->BWTransformFilter->SetTransform(this->BWTransform);this->BWTransformFilter->SetInputData(this->BWPolyData);this->BWMapper = vtkPolyDataMapper2D::New();this->BWMapper->SetInputConnection(this->BWTransformFilter->GetOutputPort());this->BWActor = vtkActor2D::New();this->BWActor->SetMapper(this->BWMapper);this->BorderProperty = vtkProperty2D::New();this->BWActor->SetProperty(this->BorderProperty);

通过两个vtkCoordinate对象约束矩形的左下角点和右上角点。

  this->PositionCoordinate = vtkCoordinate::New();this->PositionCoordinate->SetCoordinateSystemToNormalizedViewport();this->PositionCoordinate->SetValue(0.05, 0.05);this->Position2Coordinate = vtkCoordinate::New();this->Position2Coordinate->SetCoordinateSystemToNormalizedViewport();this->Position2Coordinate->SetValue(0.1, 0.1); // may be updated by the subclassthis->Position2Coordinate->SetReferenceCoordinate(this->PositionCoordinate);

在每次Render的时候，获取当前的Display坐标对原始PolyData数据进行Transform，即可看到一个一直处于视平面的矩形框。

    // Set things upint* pos1 = this->PositionCoordinate->GetComputedViewportValue(this->Renderer);int* pos2 = this->Position2Coordinate->GetComputedViewportValue(this->Renderer);// If the widget's aspect ratio is to be preserved (ProportionalResizeOn),// then (pos1,pos2) are a bounding rectangle.if (this->ProportionalResize){}// Now transform the canonical widget into display coordinatesdouble size[2];this->GetSize(size);double tx = pos1[0];double ty = pos1[1];double sx = (pos2[0] - pos1[0]) / size[0];double sy = (pos2[1] - pos1[1]) / size[1];this->BWTransform->Identity();this->BWTransform->Translate(tx, ty, 0.0);this->BWTransform->Scale(sx, sy, 1);this->BuildTime.Modified();

保持位置不变的原因：每次旋转或移动渲染窗口时，都重新获取两个vtkCoordinate对象的ViewPort坐标系下的坐标，并对其进行重新绘制。

3.2 vtkCaptionActor2D