code: def projectionMatrix(self, region=None):
      if region is None:
          region = (0, 0, self.deviceWidth(), self.deviceHeight())
  
      x0, y0, w, h = self.getViewport()
      dist = self.opts["distance"]
      fov = self.opts["fov"]
      nearClip = dist * 0.001
      farClip = dist * 1000.0
  
      r = nearClip * tan(0.5 * radians(fov))
      t = r * h / w
  
      ## Note that X0 and width in these equations must be the values used in viewport
      left = r * ((region[0] - x0) * (2.0 / w) - 1)
      right = r * ((region[0] + region[2] - x0) * (2.0 / w) - 1)
      bottom = t * ((region[1] - y0) * (2.0 / h) - 1)
      top = t * ((region[1] + region[3] - y0) * (2.0 / h) - 1)
  
      tr = QtGui.QMatrix4x4()
      tr.frustum(left, right, bottom, top, nearClip, farClip)
      return tr
  
imports: from OpenGL.GL import *
  import OpenGL.GL.framebufferobjects
  from math import cos, radians, sin, tan
  import numpy
  from ..None import Vector
  from ..None import functions
  from ..None import getConfigOption
  from ..Qt import QtCore, QtGui, QtWidgets
label_desc: Use image node_id 12 for calling the GLViewMixin obj's underlying member method code with example usage: obj.projectionMatrix(region) and returns: tr