I've been building a staircase tool and one thing I noticed that is a bit annoying is how I can't set negative scales to mirror a static mesh. When I try, the normals of the instanced mesh get inverted.



As a result I need to play tricks with my tileset to allow for as little amount of pieces as possible (because left and right winding can't always be flipped.

I can't however do this for my staircases, as an example I have a winding staircase set of 3 models in the clockwise direction.
But because I can't invert my mesh, I have 3 more for the counter-clockwise direction.



Strangely enough the Unreal Engine 4 does support inverted scale for meshes.
I can set the scale value of any static mesh to -1 and it will simply mirror itself, but its normals will remain intact.

I noticed how the meshes generated by the H engine are clumped together as instanced static meshes.
Is the inverted normals an issue with the import behavior from unreal or an oversight ?


Sincerely,
Erwin Heyms

in matertial , twosidesign to lerp (0,0,-1)(0,0,1) to normal