Yes, as @IvanKolev said:
We cannot reference a face as a root surface position while also flipping its normal. We'd need an extra "flip normal" flag in <code>SurfacePosition</code> struct and potentially deal with myriad of issues which stem from that.
Even in our projects, we most often created full-fledged meshes for the wings or simply duplicated the face to flip its normals and then began working. But most commonly, it’s a complete wing mesh, like in this project of mine: https://www.artstation.com/artwork/XgLPaL for IXOR VFX.
Just remember this rule as the correct topology. =)
Thank you and have a great day
Best regards,
Andrew.
