[Blender ] Head apart from the body? best practice for animation ? or just for render purpose ?

rafastrip

Hi, I am working on a 3D model in blender , I would like to use a good practice for Animation (game animation) to be specific , I have seen many tutorials on youtube where people use to separate the Head from the body (or torso or whatever) a single objects , but in many case I found videos for render process (Marmoset, Cycles render, Houdini ) etc... I am interesting in Animation , but also I love render process , I am wondering about the resolution and of course (gaps...) yeah gaps.... If I separate the Head mesh (LP_head.xx) from the rest of the body I will have a very good space for making UV-mapping and excelent texture process per body's part island.... however... if my character will move his arms Up and down... should I use separate head from the body?? I mean, this practice is very useful for rendering....but is good practice for animation? consideration moving shoulder ...  Maybe it is sounds very logic or weird question ... but , I need good game resolution too and at the same time make clean animation with no gaps. .. 
here it is a picture of the separate mesh (Edge split tool) . Thanks .

RN

Hi. See this:
http://polycount.com/discussion/comment/2464105/#Comment_2464105

Obscura

If the face is going to be animated in any way(didnt count rigged face, I believe that is very uncommon in real time applications, but feel free to correct me if this statement is incorrect), it must have to be separated, because otherwise your morph targets/ blend shapes would need to have a lot of unnecessary geometry. You will see in the link above, that the seam is hidden by simply matching the vertex normals.

rafastrip

ok...I just think it was for render purpose.... however I use to join  the head to the body as one single objects but differents Material ID (specially for create separate UV space and not deal with overlapping or blurred maps when I knock down the resolution for testing in Unreal or Unity ) ,  I lost resolution I know in some situation , because I use only 1 texture space for both part... however I can create ID materials on Painter or even In blender and create texture for both pieces (consideration both pieces = 1 object) ... I do not think if it is a good practice to create "edge split" for separte the head from the body and keep the position of this piece...however I need practice in animation to not deal with gaps , holes in my meshes .  Does blender support some feature to make a polish job ? thanks for your time dude.

[Edited]

I do not how to make this process (the link above) ...the video is very quick and I can not understand what's he is doing , tranfer my vertex normal of my model ? to the same model? or duplicate...well I must find a solution because I ve very noticible seams between my neck's character and his body...
 (I do not separate the mesh , I just only export in fbx output all of my Lowpoly assets to SP , with and ID material for every pieces, but the object at least , head and body , they seems to be separate , but they are together, is the material ID contribution a good rule for exportin in SP )

this Pictures reveals the bad process of mine.