Textures and decals are both affected by gaps and whatnot.
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I take it these are meant to be displays which means it would be preferred that the image isn’t affected by light but unfortunately this is the only option for getting gaps in the image without having to alter the image itself.
I’ve used Decals on Unions with gaps and haven’t noticed them being affected, as long as the faces are somewhat close to 90 degrees the Decal only gets placed on one of the 6 ‘faces’ of the Union.
I mean it can really be either, I just prefer surfacegui because then I can control the fitment to be crop, etc. and then I can add other layers on top of it to make it more realistic like a screen