如何在FreeCAD的Coin3D场景中使用OpenGL进行绘图？

需求与前期准备 #

希望在FreeCAD衔接Coin3D与OpenCascade场景的QuarterWidget中，直接使用OpenGL绘制新对象（不依赖Coin3D等库），采用Python开发（也接受C++示例）。已通过以下代码获取到相关对象：

def GetQuarterWidget(self): #From FreeCAD forum
    views = []
    self.mainWindow=Gui.getMainWindow()
    for w in self.mainWindow.findChild(QtGui.QMdiArea).findChildren(QtGui.QWidget):
        if w.inherits("SIM::Coin3D::Quarter::QuarterWidget"):
            views.append(w)
    return views

def getMdiWindow(self):  #From FreeCAD forum
    mw = Gui.getMainWindow()
    mdi = mw.findChild(PySide2.QtWidgets.QMdiArea)

已实现的三角形绘制代码 #

已成功绘制三角形，代码如下：

from OpenGL.GL import *
from OpenGL.GLU import *
import PySide2
import FreeCADGui as Gui
import pivy.coin as coin
import PySide.QtCore as QtCore
import PySide.QtGui as QtGui
from PySide2.QtOpenGL import *
from OpenGL.WGL import *

def drawOpenGl(arg1,arg2):
    glTranslatef(-2.5, 0.5, -6.0)
    glColor3f( 1.0, 1.5, 0.0 )
    glPolygonMode(GL_FRONT, GL_FILL)
    glBegin(GL_TRIANGLES)
    glVertex3f(2.0,-1.2,0.0)
    glVertex3f(2.6,0.0,0.0)
    glVertex3f(2.9,-1.2,0.0)
    glEnd()

def drawsomething():
    w_view = Gui.ActiveDocument.ActiveView
    Root_SceneGraph = w_view.getSceneGraph()
    calback_=coin.SoCallback()
    calback_.setCallback(drawOpenGl)
    Root_SceneGraph.addChild(calback_)

drawsomething()

依赖安装步骤 #

需通过FreeCAD自带的Python环境安装PyOpenGL，执行命令：

FREECAD_DIR/bin/Scripts/pip install pyopengl

内容的提问来源于stack exchange，提问作者Ku Mu