三維可視化系統的建立依賴于三維圖形平臺， 如 OpenGL、VTK、OGRE、OSG等， 傳統的方法多采用OpenGL進行底層編程，即對其特有的函數進行定量操作， 需要開發人員熟悉相關函數， 從而造成了開發難度大、 周期長等問題。VTK、 ORGE、OSG等平臺使用封裝更好的函數簡化了開發過程。下面將使用Python與VTK進行機器人上位機監控界面的快速原型開發。

完整的上位機程序需要有三維顯示模塊、機器人信息監測模塊（位置/角度/速度/電量/溫度/錯誤信息...）、通信模塊（串口/USB/WIFI/藍牙...）、控制模塊等功能模塊。三維顯示模塊主要用于實時顯示機器人的姿態（或位置）信息。比如機器人上肢手臂抬起，程序界面中的虛擬機器人也會同時進行同樣的動作。三維顯示模塊也可以用于對機器人進行控制，實現良好的人機交互。比如在三維圖像界面中可以點擊拾取機器人某一關節，拖拽部件(肢體)控制真實的機器人完成同樣的運動。Aldebaran Robotics的圖形化編程軟件Choregraphe可以完成上述的一些功能對NAO機器人進行控制。

對于簡單的模型可以自己編寫函數進行創建，但這種方法做出來的模型過于簡單不夠逼真。因此可以先在SolidWorks、Blender、3DMax、Maya、Rhino等三維設計軟件中建立好模型，然后導出為通用的三維文件格式，再使用VTK將其讀入并進行渲染。

在SolidWorks等三維設計軟件中設計好機器人的大臂（upperarm）和小臂（forearm），然后創建裝配體如下圖所示。在將裝配體導出為STL文件前需要注意幾點：

1. 當從外界讀入STL類型的模型時，其會按照它內部的坐標位置進行顯示，因此它的位置和大小是確定的。為了以后的定位以及移動、旋轉等操作的方便，需要先在SolidWorks中創建一個坐標系。如下圖所示，坐標系建立在大臂關節中心點。

2. 如果將裝配體整體輸出為一個STL文件，則導入VTK后無法控制零部件進行相對運動。因此，需要將裝配體各可動部件分別導出。

在SolidWorks的另存為STL對話框中，點開輸出選項卡，如下圖所示。注意之前提到的幾點：如果勾選“在單一文件中保存裝配體的所有零部件”則會將整個裝配體導出為一個STL文件，否則就是分別命名的兩個STL文件；輸出坐標系下拉列表中選擇之前創建的坐標系1，并勾選“不要轉換STL輸出數據到正的坐標空間”。

下面的Python代碼簡單實現了一個2自由度機械臂的三維仿真，可以拖動滑塊或按鍵盤上的方向鍵控制肩關節或肘關節運動。當然程序還存在一些問題有待完善...

#!/usr/bin/env python

import vtk

import math

from vtk.util.colors import *

filenames = ["upperarm.stl","forearm.stl"]

dt = 1.0 # degree step in rotation

angle = [0, 0] # shoulder and elbow joint angle

renWin = vtk.vtkRenderWindow()

assembly = vtk.vtkAssembly()

slider_shoulder = vtk.vtkSliderRepresentation2D()

slider_elbow = vtk.vtkSliderRepresentation2D()

actor = list() # the list of links

# Customize vtkInteractorStyleTrackballCamera

class MyInteractor(vtk.vtkInteractorStyleTrackballCamera):

def __init__(self,parent=None):

self.AddObserver("CharEvent",self.OnCharEvent)

self.AddObserver("KeyPressEvent",self.OnKeyPressEvent)

# Override the default key operations which currently handle trackball or joystick styles is provided

# OnChar is triggered when an ASCII key is pressed. Some basic key presses are handled here

def OnCharEvent(self,obj,event):

pass

def OnKeyPressEvent(self,obj,event):

global angle

# Get the compound key strokes for the event

key = self.GetInteractor().GetKeySym()

# Output the key that was pressed

#print "Pressed: " , key

# Handle an arrow key

if(key == "Left"):

actor[1].RotateY(-dt)

if(key == "Right"):

actor[1].RotateY(dt)

if(key == "Up"):

assembly.RotateY(-dt)

angle[0] += dt

if angle[0] >= 360.0:

angle[0] -= 360.0

slider_shoulder.SetValue(angle[0])

if(key == "Down"):

assembly.RotateY(dt)

angle[0] -= dt

if angle[0] < 0.0:

angle[0] += 360.0

slider_shoulder.SetValue(angle[0])

# Ask each renderer owned by this RenderWindow to render its image and synchronize this process

renWin.Render()

return

def LoadSTL(filename):

reader = vtk.vtkSTLReader()

reader.SetFileName(filename)

mapper = vtk.vtkPolyDataMapper() # maps polygonal data to graphics primitives

mapper.SetInputConnection(reader.GetOutputPort())

actor = vtk.vtkLODActor()

actor.SetMapper(mapper)

return actor # represents an entity in a rendered scene

def CreateCoordinates():

# create coordinate axes in the render window

axes = vtk.vtkAxesActor()

axes.SetTotalLength(100, 100, 100) # Set the total length of the axes in 3 dimensions

# Set the type of the shaft to a cylinder:0, line:1, or user defined geometry.

axes.SetShaftType(0)

axes.SetCylinderRadius(0.02)

axes.GetXAxisCaptionActor2D().SetWidth(0.03)

axes.GetYAxisCaptionActor2D().SetWidth(0.03)

axes.GetZAxisCaptionActor2D().SetWidth(0.03)

#axes.SetAxisLabels(0) # Enable:1/disable:0 drawing the axis labels

#transform = vtk.vtkTransform()

#transform.Translate(0.0, 0.0, 0.0)

#axes.SetUserTransform(transform)

#axes.GetXAxisCaptionActor2D().GetCaptionTextProperty().SetColor(1,0,0)

#axes.GetXAxisCaptionActor2D().GetCaptionTextProperty().BoldOff() # disable text bolding

return axes

def ShoulderSliderCallback(obj,event):

sliderRepres = obj.GetRepresentation()

pos = sliderRepres.GetValue()

assembly.SetOrientation(0,-pos,0)

renWin.Render()

def ElbowSliderCallback(obj,event):

sliderRepres = obj.GetRepresentation()

pos = sliderRepres.GetValue()

actor[1].SetOrientation(0,-pos,0)

renWin.Render()

def ConfigSlider(sliderRep, TitleText, Yaxes):

sliderRep.SetMinimumValue(0.0)

sliderRep.SetMaximumValue(360.0)

sliderRep.SetValue(0.0) # Specify the current value for the widget

sliderRep.SetTitleText(TitleText) # Specify the label text for this widget

sliderRep.GetSliderProperty().SetColor(1,0,0) # Change the color of the knob that slides

sliderRep.GetSelectedProperty().SetColor(0,0,1) # Change the color of the knob when the mouse is held on it

sliderRep.GetTubeProperty().SetColor(1,1,0) # Change the color of the bar

sliderRep.GetCapProperty().SetColor(0,1,1) # Change the color of the ends of the bar

#sliderRep.GetTitleProperty().SetColor(1,0,0) # Change the color of the text displaying the value

# Position the first end point of the slider

sliderRep.GetPoint1Coordinate().SetCoordinateSystemToDisplay()

sliderRep.GetPoint1Coordinate().SetValue(50, Yaxes)

# Position the second end point of the slider

sliderRep.GetPoint2Coordinate().SetCoordinateSystemToDisplay()

sliderRep.GetPoint2Coordinate().SetValue(400, Yaxes)

sliderRep.SetSliderLength(0.02) # Specify the length of the slider shape.The slider length by default is 0.05

sliderRep.SetSliderWidth(0.02) # Set the width of the slider in the directions orthogonal to the slider axis

sliderRep.SetTubeWidth(0.005)

sliderRep.SetEndCapWidth(0.03)

sliderRep.ShowSliderLabelOn() # display the slider text label

sliderRep.SetLabelFormat("%.1f")

sliderWidget = vtk.vtkSliderWidget()

sliderWidget.SetRepresentation(sliderRep)

sliderWidget.SetAnimationModeToAnimate()

return sliderWidget

def CreateGround():

# create plane source

plane = vtk.vtkPlaneSource()

plane.SetXResolution(50)

plane.SetYResolution(50)

plane.SetCenter(0,0,0)

plane.SetNormal(0,0,1)

# mapper

mapper = vtk.vtkPolyDataMapper()

mapper.SetInputConnection(plane.GetOutputPort())

# actor

actor = vtk.vtkActor()

actor.SetMapper(mapper)

actor.GetProperty().SetRepresentationToWireframe()

#actor.GetProperty().SetOpacity(0.4) # 1.0 is totally opaque and 0.0 is completely transparent

actor.GetProperty().SetColor(light_grey)

'''

# Load in the texture map. A texture is any unsigned char image.

bmpReader = vtk.vtkBMPReader()

bmpReader.SetFileName("ground_texture.bmp")

texture = vtk.vtkTexture()

texture.SetInputConnection(bmpReader.GetOutputPort())

texture.InterpolateOn()

actor.SetTexture(texture)

'''

transform = vtk.vtkTransform()

transform.Scale(2000,2000, 1)

actor.SetUserTransform(transform)

return actor

def CreateScene():

# Create a rendering window and renderer

ren = vtk.vtkRenderer()

#renWin = vtk.vtkRenderWindow()

renWin.AddRenderer(ren)

# Create a renderwindowinteractor

iren = vtk.vtkRenderWindowInteractor()

iren.SetRenderWindow(renWin)

style = MyInteractor()

style.SetDefaultRenderer(ren)

iren.SetInteractorStyle(style)

for id, file in enumerate(filenames):

actor.append(LoadSTL(file))

#actor[id].GetProperty().SetColor(blue)

r = vtk.vtkMath.Random(.4, 1.0)

g = vtk.vtkMath.Random(.4, 1.0)

b = vtk.vtkMath.Random(.4, 1.0)

actor[id].GetProperty().SetDiffuseColor(r, g, b)

actor[id].GetProperty().SetDiffuse(.8)

actor[id].GetProperty().SetSpecular(.5)

actor[id].GetProperty().SetSpecularColor(1.0,1.0,1.0)

actor[id].GetProperty().SetSpecularPower(30.0)

assembly.AddPart(actor[id])

# Add the actors to the scene

#ren.AddActor(actor[id])

# Also set the origin, position and orientation of assembly in space.

assembly.SetOrigin(0, 0, 0) # This is the point about which all rotations take place

#assembly.AddPosition(0, 0, 0)

#assembly.RotateX(45)

actor[1].SetOrigin(274, 0, 0) # initial elbow joint position

ren.AddActor(assembly)

# Add coordinates

axes = CreateCoordinates()

ren.AddActor(axes)

# Add ground

ground = CreateGround()

ren.AddActor(ground)

# Add slider to control the robot

sliderWidget_shoulder = ConfigSlider(slider_shoulder,"Shoulder Joint", 80)

sliderWidget_shoulder.SetInteractor(iren)

sliderWidget_shoulder.EnabledOn()

sliderWidget_shoulder.AddObserver("InteractionEvent", ShoulderSliderCallback)

sliderWidget_elbow = ConfigSlider(slider_elbow,"Elbow Joint", 160)

sliderWidget_elbow.SetInteractor(iren)

sliderWidget_elbow.EnabledOn()

sliderWidget_elbow.AddObserver("InteractionEvent", ElbowSliderCallback)

# Set background color

ren.SetBackground(.2, .2, .2)

# Set window size

renWin.SetSize(600, 600)

# Set up the camera to get a particular view of the scene

camera = vtk.vtkCamera()

camera.SetFocalPoint(300, 0, 0)

camera.SetPosition(300, -400, 350)

camera.ComputeViewPlaneNormal()

camera.SetViewUp(0, 1, 0)

camera.Zoom(0.4)

ren.SetActiveCamera(camera)

# Enable user interface interactor

iren.Initialize()

iren.Start()

if __name__ == "__main__":

CreateScene()

下面是使用MFC搭建的機器人上位機監控平臺，可以實現上述的一些基本功能。這個GIF動畫使用開源軟件ScreenToGif生成，非常好用！

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