Q:

How do I remove the line gap things after separating some meshes? (apple peeling)

I'm trying to turn this apple into a monster like thing. I've marked 4 parts that are showed in the images, which are the parts that will peel off and the apple will move on 4 legs during my future animation. Problem is, when I separated by selection for the meshes, the black lines around the areas appeared, they are not needed and I have no idea how to fix it. 

A:

Using the Data Transfer modifier to transfer vertex normals from an uncut whole apple to an apple that has been cut up into several seperate objects, (slices).

To the whole uncut apple object, apply any modifers.
Open up the Object Data Properties panel and enable the Auto Smooth option.

Give this apple object the name apple_whole. 

In Object mode make a copy of apple_ whole.
Hide the "apple_whole"object.
Give the newly created object the name "Slice"
Add a Data Transfer modifier to the slice object.
The Source Object will be apple_whole. 
Enable Face Corner Data and select the Projected Face Interpolation option. 
Select Custom Normals.  
In Edit mode selected the different slices and separate them into separate objects.

The the apple should now be sliced up into a number of different objects and each of these objects should have the Data Transfer modifier. 

If you look carefully in the screenshots below you should be able to see the difference between a sliced apple without the Data Transfer modifier(on the left) and the sliced apple with the modifier (on the right).

Note; Thankyou to BGibonus (model) and AGF81 (texture) on Blend Swap for providing the Cylcle_compatable apple, free of charge, that was used in this post.

