vtk3———System Overview

System Architecture

the visualization pipeline

• The visualization pipeline is used to acquire or create data, process that data, and either write the results to a file or pass the results to the rendering engine for display.
• Algorithms and data objects are connected together to form visualization pipelines.
  
  • vtkDataObject
  • vtkAlgorithm
• the construction of the visualization pipeline
  
  • methods :aFilter->SetInputConnection( anotherFilter->GetOutputPort() );
  • a lazy evaluation scheme ((executes only when when the data is requested)
  • only those objects compatible with one another can fit together with the SetInputConnection() and GetOutputPort() methods
  • decide whether to cache, or retain, the dataobjects once the pipeline has executed.
• Pipeline Execution: do not need to manually invoke Update() because the filters are connected into visualization pipeline.(when rendering,data is requested,pipeline execution)
• Image Precessing: Almost all algorithms in the imaging pipeline are
  multithreaded and are capable of streaming data in pieces to satisfy a user-specified memory limit

the rendering engine

• The rendering engine is responsible for creating a visual representation of the data.
• vtkProp – know position size and orientation
  
  • 3D vtkActor(geometric data) and vtkVolume(volumetric data)
  • 2D vtkActor2D
  • 2D annotation vtkScalarBarActor
  • vtkImageActor (used to display an image)
  • vtkPieChartActor
  • vtkFollower
  • vtkLODActor
• vtkAbstractMapper
• vtkProperty and vtkVolumProperty
• vtkCamera
• vtkLight
• vktRender
• vtkRenderWindow
• vtkRenderWindowInteractor
• vtkTransform.
• vtkLookupTable, vtkColorTransferFunction, and vtkPiecewiseFunction.

Low-Level Object Model

• root class vtkObject vtkObjectBase
• new() —— delete()
• 引用计数 —— Set…(..)
• GetClassName()
• IsA(” “) / SafeDownCast()
• Print(cout)

Create An Application

• using the Subject/Observer and Command design pattern
• AddObserver() method that can be used to setup callbacks

• compulsory type conversion operator:reinterpret_cast

  vtkRenderer *renderer = reinterpret_cast<vtkRenderer*>(caller); vtkRenderer *ren = vtkRenderer::SafeDownCast(caller);

• create your subclass of vtkCommand and add an observer that will call your command on certain events.
  (/Example/Tutorial/step2/Cxx——class vtkMyCallback : public vtkCommand)