Waterfall_13
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If I understand correctly, it refers to polygons with smoothing, that is, with rounded edges. This is not possible in the game. I think it is worth trying to solve the problem with texturing.
I can only assume that the texturing was done in Blender with rounded polygons. When exporting, the rounding disappeared, and the texture was slightly stretched in places, here and there, and that's why the difference is visible. These are just my assumptions.
It would be better to do the texturing on the model on the left, or not use smoothing.
I did the texturing in Substance Painter
And in Blender, I baked textures from the high-poly to the low-poly model
The trick is that this smooth shading setting is quite adequately transferred from Blender to Substance, Unity, and Unreal Engine 4. The problem here is clearly that the "shade smooth" setting was lost. The texture was applied correctly, but the shape is angular because the correct shading is missing.