How to make the outline shading?

Here are some examples of what i want it to look like. I mean these… outline shadows? (this is especially noticeable where meshes are in the background of skysphere). I think that similar effect is achievable in Photoshop by blurring a copy of an image on the upper layer and setting it’s opacity to 50% (but it’s not exactly the same effect). Also if you know the name of this effect please let me know