Extrude Normals flipped

Don’t know if this is a bug/feature/weird thing.

When extruding a simple rectangle SOP, the normals are pointing inwards on the new faces. When compute normals is selected it all just looks a bit wrong, like the the normals are computed at 45 on each corner.

Could there maybe be a “flip normals on extruded surfaces” option. the points SOP with add normals set to []*-1 works but then you have to run it through a merge to get it all back together.

Thanks for the report. I agree that the normals seem flipped from what they should be. I’ll take a look into it and see if there’s something we should fix.

A couple things that you might find useful:

  • If you’re not aware, you can visualize the normals by right clicking on an active 3D viewer, choosing Display Options and checking the ‘Point normals’ box on the ‘Guides and Markers’ page. This will display the normals for your geometry so don’t have to guess how they are facing.
  • By default, the extrude sop will smooth the side surfaces of the extruded object so that the normals are at 45 degrees like you mentioned; however, if you enable the ‘Cusp Polygonal Sides’ toggle then it will only smooth sides that are less than the given angle. This will create a box with hard edges in your case.
  • If you set the depth scale to -1, it will flip the extrusion so that the normals on the sides point outwards; however, it also flips the front and back normals so this probably won’t be useful in your case.