Here is an example: Babylon.js Playground
When I apply a normal rectangular texture to a sphere, it get mirror flipped.
I need to set frontUVs: new BABYLON.Vector4(1, 1, 0, 0) as line 20 in the playground to make it right.
I’m wondering what caused this issue. Is this a bug? Big thanks.
This is how the UV have been layout by default and it would be a breaking change to fix it now 
In your case it is simple enough to not flip the texture I guess https://playground.babylonjs.com/#K6M44R#2521
Thank you for responding.
The texture is not y-flipped, but mirror-flipped. So invertY only is not enough, you should also make it left-right flip. That why I said it’s wired. You must set the frontUVs.
I know that it’s because the uv unwrapping makes it work like this. What I want to know is whether you set UV coordinate like this deliberately. Thank you.
The backwards compatibility is such a big thing, huge legacy 
As this would go back in history a lot, let me summon @Deltakosh the babylon.js daddy
It came from initial implementation which was aligned with my old Nova exporter for max And it was using Max way of doing thing at that time
Thank you so much for your reply. I got it. 
Do you think there need an option to make the texture be unwrapped in a right direction, like the wrap option in MeshBuilder.CreateBox @Deltakosh
I do not think so as we can already pass the UVs in. There are too many ways to layout.
Hi, may I ask more about the ways to layout? As I only figured out one way, which is using the frontUVs.
I have seen some trying to see the sphere as a blown up cube so with faces for instance or only 4 repeats quarter like for instance.
Sorry I didn’t get it, lol. Still might be a little hard for me.
wrap is such an appropriate and useful option for freshman like me, in this condition. 