Reverse Normals

The normal direction of surfaces is critical to how offset compensation is applied to your measurements. An incorrectly-oriented surface normal can lead to dramatically incorrect analysis results. CAD surfaces should always have their normals facing away from the material of the part. That is, the side on which you approach the surface with a probe must be defined as the positive side of the surface.

The use of surface backside coloring (see Display Colors) enables you to determine if any surface normals are reversed. Whenever you import a CAD model, you should therefore check to ensure that surface normals are correct, and any incorrect normals should be fixed.

There are several methods for flipping surface normals: indicating point on positive side, reversing normals, and auto-reversing from viewpoint. All of these methods require a surface to be dissected into its individual surface faces before they are reversed.

NOTE. Some surfaces are imported as solid /closed models and cannot have their surface normals reversed. For those surfaces separate CAD faces must first be built, using tools such as Dissect Selected Surface.

 

Indicate Point on Positive Side

One method for correcting surface normals is to use a reference point as an indicator for whether that point should end up on the positive or negative side of a surface. This is similar to some metrology software that expects an additional measured point to indicate the direction of offsets for measured geometric surfaces.

 

Reversing Surface Normals

The most straightforward method for reversing surface normals is to explicitly select the surfaces you’d like to reverse. The normal direction of each selected surface will be flipped. This will flip the normals for each face included in the selected surface.

 

Auto-Reversing Surface Normals from Viewpoint

NormalsSA can use the current view orientation to automatically reverse a set of surface faces. This has the advantage of reversing a large number of surfaces at once, without requiring you to select the specific surfaces you’d like to fix.

With this command, you orient the view so that you can see the surfaces you’d like to correct. You then select these surfaces, and the key is that you can also select surfaces which are already facing the proper direction. SA will go through each selected surface, determine if it’s visible from the current viewpoint, and then reverse it if its normal does not generally point toward the viewpoint.

 

Reverse Face Normals

Use this command to individually select and reverse surface faces from a model.