Can't Detect Object with Shape Detection Function in NI Vision Assistant

Updated May 15, 2023

Reported In


  • Vision Assistant
  • Vision Development Module

Issue Details

I am using the NI Vision Assistant to try to identify particular shapes (rectangle, line, circle, ellipse) in my captured image. I am applying the Shape Detection function but am not able to detect my shape. Why?


Using the Context Help (Help  >> Context Help) you can find extra information on the different customizable parameters in the Shape Detection step. You should try different values for these parameters to detect your shape. Here are a few parameters to check to ensure you can properly detect shapes in your image:
  • Ensure your Region of Interest includes your shape that you wish to detect. 
  • Ensure the image is gray-scale. A gray-scale image is required for the shape detection function to work properly. To do this, apply a Color Plane Extraction prior to calling Shape Detection in Vision Assistant.
  • In the Shape tab of the Shape Detection function, ensure the min and max dimensions in the Descriptor section are appropriately sized for the image you are trying to detect.
  • For better results, you can enable searching for Rotated, Scaled, and Occluded matches in the Settings tab of the Shape Detection function.
  • If you are receiving too many (or too few) shapes detected, you can modify the Minimum Score in the Settings tab. A higher value will detect the most correct/perfect shapes, and a lower value will return shapes that were not as perfect.