Hi,
If it's data on every Primitive why there is no data showing on the Geometry Spreadsheet?

And why when adding "reverse" node (in U) after the flipped Primitive normals it get reversed? why U? isn't U for UVs?
Sorry I am new to Houdini.

I think it's calculated on the fly but I might be wrong. prim_normal() can access it.

Soothsayer
I think it's calculated on the fly but I might be wrong. prim_normal() can access it.

Thanks Soothsayer.
I think it's important to have this data available on the Geometry Spreadsheet, at least there is an option to show it.
Because it's difficult to troubleshoot the error (if any) with no data.

I spent more than 3 hours to find a solution to reverse the flipped Primitive Normals because you can't group it procedurally.

The polygonal normals are implicit
Always derived from polygon winding using I think left hand rule

Reverse Sop in U will reverse winding order of the polygon therefore the computed normal will naturally point to the opposite direction
U and V parametric coordinates have nothing to do with UV attribute other than the name, the same way as this geometric implicit normal is independent from potential primitive N attribute

- you can visualize reversed normal by turning on tinting blackfaces
- seeing values in geo spreadsheet will arguably not help you know whether it's reversed or not
- there are procedural ways to detect or flip reversed polygons for specific cases like watertight meshes or occasional flipped polys in continuous mesh, or simple cases like semi planar meshes with known desired overall direction but also many other cases may be ambiguous