If you have been using XOR for reverse engineering and XOV for inspection, sometimes you may be confused why the results of deviation by the Accuracy Analyzer of XOR and Whole Deviation of XOV are different. As you know, XOR is the software for reverse engineering and XOV is the software for inspection. Even though you try to calculate deviation using the same Design data and Scan data, the results would be different because of the difference in calculation method as shown in the image below.

Through this technical tip, you will understand how these two applications calculate deviation and why the results of deviation are different.

Difference in calculation method

Whole Deviation of XOV is focused for checking how much the scanned points are close to the nominal data. So the application measures the gap that the scanned points have among the nominal data. In other words, the application tries to project the scanned points onto the nominal data and calculates its gap as shown in the image below.

But the Accuracy analyzer of XOR is focused on checking how much the modeled data, which is designed by several reverse engineering tools, is close to the real scanned object. So the application measures gap that the modeled data have among the real scanned object. In other words, the application tries to tessellate modeled data so that it can project it onto the scanned data and then it calculates the gap as shown in the image below.

Since our interest of deviation calculation is different in both applications, the results of deviation are calculated in a different manner based on the respective interest.

Note

You can see the difference in the results of deviation in XOR by setting the modeled data as reference in Mesh Deviation (Measure > Mesh Deviation).