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Does low poly and high poly uv's needs to be same? Baking high to low

I am a junior texture artist but still looong way to go, Still a learner and want to know about the baking.
1. Does the high poly uv's needs to be the same as the low poly uv's? 
I know the answer is no, can you please explain it more or can you please link to a detailed article or something?
Whether it's x normal, marmoset , painter or z brush we don't need the uv's for the high poly mesh? 
Please correct me if i am wrong, i want to deeply understand this.
Help would be greatly appreciated.


  • poopipe
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    poopipe grand marshal polycounter
    UVs on the high poly aren't relevant to the bake. 

    as a very simple explanation of what happens...
    The baked textures are generated by drawing lines from the surface of the low poly mesh and capturing information where those lines cross the high poly. 

    there's a lot more to it than that but a full explanation would mean typing a lot of words and understanding it would require a bunch of supporting knowledge

  • gnoop
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    gnoop sublime tool
    UV on hi res mesh is not necessary at all in typical baking scenario but  could be helpful in some special cases IMO.  
        When  your model  is a mess of ropes , small details like  rows of bolts next to each other  or hordian knot of pipes  etc.   So in such case  it might be more time efficient  to bake object space normal map on hi res itself  and then re-bake it into tangent one  for low res  rather than  dealing with splitting and re-naming gazillion parts  or "exploding' everything.     Especially when your hi res model is sub-d  of low res one    or when you use  CAD soft for modelling and sort of having UV already that need just to be packed  .
    You can use object space texture  as "directional map" texture source  to rebake into tangent space normal map  in Substance Designer or use Blender for this. The trick is just to figure out axis colors . Xnormal could do it too as far as i remember.
    It's  an archaic way  but I still find it more convenient in some cases .

  • Klunk
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    Klunk ngon master
    As above, but 2 sets of UV's on the low res model are a thing though, if you want to render a texture from on one set to another (used to be common practise for removing seams when 3d paint packages were not available).
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