title: Stereo Webcam Depth Detection
body: <p>I'm newbie to computer vision.
  I'm trying to calculate depth from stereo webcam.
  I flowed this steps:</p>
  
  <ul>
  <li>Camera calibration:Calibrate each camera individually,i got Rms 0.2 and 0.18 then i calibrate both cameras (Rms:0.8) using openCv3.</li>
  <li>Calculate Disparity map using  ximgproc and opencv3 (create left matcher the right matcher and then createDisparityWLSFilter)</li>
  <li>detect and object (using colors)</li>
  <li>Use this equation: depth=base_line*focal_length/disparity to get depth
  I got strange values,i even tried to used cv2.reprojectImageTo3D but it gave same problem.</li>
  </ul>
  
  <p>I cannot have fix values. when the ball is farther the depth is smaller.
  I didn't understand the (x,y,z) given from the 3D reconstitution<br>
  here is my code.
  Please help </p>
  
  <h1>code</h1>
  
  <p>while(True):
      if not (left.grab() and right.grab()):
          print("No more frames")
          break
      _, leftFrame = left.retrieve()
      _, rightFrame = right.retrieve()
      leftFrame = cv2.remap(leftFrame,leftMapX,leftMapY,cv2.INTER_LINEAR)
      rightFrame = 
      cv2.remap(rightFrame,rightMapX,rightMapY,cv2.INTER_LINEAR)</p>
  
  <pre><code>displ = left_matcher.compute(rightFrame,leftFrame).astype(np.float32)/16
  dispr = right_matcher.compute(leftFrame ,rightFrame ).astype(np.float32)/16
  displ = np.int16(displ)
  dispr = np.int16(dispr)
  filteredImg=None
  filteredImg = wls_filter.filter(displ, rightFrame, None, dispr)  # important to put "imgL" here!!!
  filteredImg = cv2.normalize(src=filteredImg, dst=filteredImg, beta=0, alpha=255, norm_type=cv2.NORM_MINMAX);
  filteredImg = np.uint8(filteredImg)
  cv2.imshow('disparity', filteredImg)
  
  center=bd.ball_detection(rightFrame)
  
  points_3D = cv2.reprojectImageTo3D(filteredImg, Q)
  if center!= None:
      x= points_3D[center][0]
      y= points_3D[center][1]
      z= points_3D[center][2]
      print("1",triangulation_constant/filteredImg[center])
      print("2",x,y,z)
  </code></pre>