使用VTK与Python实现机械臂三维模型可视化

　　三维可视化系统的建立依赖于三维图形平台， 如 OpenGL、VTK、OGRE、OSG等， 传统的方法多采用OpenGL进行底层编程，即对其特有的函数进行定量操作， 需要开发人员熟悉相关函数， 从而造成了开发难度大、 周期长等问题。VTK、 ORGE、OSG等平台使用封装更好的函数简化了开发过程。下面将使用Python与VTK进行机器人上位机监控界面的快速原型开发。

　　完整的上位机程序需要有三维显示模块、机器人信息监测模块（位置/角度/速度/电量/温度/错误信息...）、通信模块（串口/USB/WIFI/蓝牙...）、控制模块等功能模块。三维显示模块主要用于实时显示机器人的姿态（或位置）信息。比如机器人上肢手臂抬起，程序界面中的虚拟机器人也会同时进行同样的动作。三维显示模块也可以用于对机器人进行控制，实现良好的人机交互。比如在三维图像界面中可以点击拾取机器人某一关节，拖拽部件(肢体)控制真实的机器人完成同样的运动。Aldebaran Robotics的图形化编程软件Choregraphe可以完成上述的一些功能对NAO机器人进行控制。

#!/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()

View Code



　　下面是使用MFC搭建的机器人上位机监控平台，可以实现上述的一些基本功能。这个GIF动画使用开源软件ScreenToGif生成，非常好用！





参考 ：

基于OpenGL的六自由度机械臂三维仿真工具的设计

03-VTK基础概念(2)

第04章-VTK基础（4）

Using VTK Interactors

VTK/Examples/Cxx/PolyData/TransformPipeline

VTK/Examples/Cxx/Visualization/DisplayCoordinateAxes

VTK/Examples/Cxx/GeometricObjects/Axes

Using VTK to Visualize Scientific Data (online tutorial)

VTK/Tutorials/Widgets

VTK/Tutorials/InteractorStyleSubclass