I made 3 models, each has own material. And after texture painting, I combined each their texture to single textures for optimization.
Currently making Mobile Game with Unity 2018 and using Mobile/BumpedSpecular shader for rendering, which is actually simplified BlinnPhong lighting model.
However after checking the result, I get weird result in some spots with Diffuse texture.
Note that Mobile/BumpedSpecular shader in Unity uses alpha channel of diffuse texture as glossiness. So after I combined those three different diffuse textures, I exported with no background(transparent background) like this:
UV mapped correctly, diffuse texture has alpha, importing alpha channel as well.
Everything seems fine, but why do I have this wrong result? First time I thought that I did something mistake, so I repeated whole process again, but still have same result, not this one, with other models also. So I thought that it was bug from Unity, actually but it wasn't, I tried with Blender and have same result.
So one thing I can know that there might be something missed in my integrated diffuse/glossiness texture. What am I missing?