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

Erwin, did you ever find a solution for this? I’m encountering the same issue and an unable to use two-sided rendering as a workaround.

Thanks to Freedmoist for that solution, this is the best way to get instanced meshes to accept negative scales in Unreal. Worked great on some vertex animated characters I'm working on.