On a sheetmetal part that was scanned from both sides, a Laser Auto Circle was created.

The Feature Extraction - Vertical clipping zone is set so it includes the part deviations, which in this case is larger than the sheetmetal thickness.

In this image, no Max incidence angle is used:

Since the normals of the scanned points are not taken into consideration, the extracted circle uses data from both sides of the part.

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In this image, a Max incidence angle of 75 degrees is used:

The estimated normal of each point in the clipping zone is compared to the Laser Auto Circle, surface theoretical vector. Points with a vector which fall outside this angle are not used for the feature calculation.