Texture Baking Without a HD Model
Substance Painter expects you to add a HD model with smooth beveled edges. If you do not have a HD model most of the generators and filters will not work correctly. I use bevels to overcome this issue.
To save time I only hard surface model a low poly model and don't create a HD model. Then I use Blender Modifiers to add bevels. When you set the Limit Method to Weight you will get full control over the beveled edges. A tool like Hard Ops will greatly speed up your workflow.
I always recommend adding a Weighted Normal Modifier last. When you use bevels Keep Shard should disabled.
Just adding a bevel modifier won't fix the curvature. This issue can be compensated by adding a Subdivion Surface Modifier after the Bevel Modifier. Depending on the model complexity the results can differ.
If the Subdivion Surface approach does not work the curvature can be blurred in Substance Painter before use. If the map is needed directly you can use an Anchor Point.
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