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Beginner questions: What all to UV map this symmetrical object

polycounter lvl 3
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Thane- polycounter lvl 3
I used 3D Studio Max to model this and im stuck on what all needs to be unwrapped and what doesn't. I know how to unwrap, but im confused about how and when i can use the symmetry modifier during this process (should i turn it off?) -also how instanced geometry comes into play? Will instanced geometry all unwrap the same and go into a game engine just fine after export into 3ds max? Is it not okay to overlap UVs? I've searched on this almost all day and can't quite find the answers.


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  • Bek
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    Bek interpolator
    You could probably watch some tutorials that cover the basics in order to figure out how the whole process comes together.

    Here's one example of such a tutorial. And another.

    To answer the overlap question now:

    Generally in a game engine a texture is repeated in both U and V axis of the texture. So if you have 6 identical cylinders you'd unwrap one and duplicate it (so they UV's are stacked). Stacked UV's are only a problem when you go to bake a normal map (and maybe some other stuff); which is why you'll often offset your duplicate pieces by 1 in either U or V or both, because the texture is repeated in those co-ordinates — but anything outside the 0,0 to 1,1 bounds isn't taken into account when baking.
  • Thane-
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    Thane- polycounter lvl 3
    Believe me, i've watched about 10 different tutorials, but all used pretty simple objects and many didn't reference whether the models were destined for a game engine or just a render, thus i never knew whether, for example, the overlapping that was featured in one of them, was okay for a game engine. Somewhere someone wrote not to overlap UVs. I had those tutorials on the list, but i thought i had it down better. :)

    So my basic guess as to how to proceed most efficiently would be:

    1.)Delete all instanced geometry and slice symetrical models in half or even quarters (like the barrel) deleting the other halfs.

    2.) UV map what is left.

    3.) After mapping, copy needed identical geometry as instances ( and their UV's will automatically be overlayed in the existing set and accounted for during obj export? )
  • Bek
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    Bek interpolator
    No idea how instances work in 3ds max but I would guess you don't need to delete the modifier; uv's will be mirrored/instanced/whatever as well. Try it out.

    Keep in mind that mirroring saves texture space (which is generally a really good idea) but also increases vert count (slightly, because more uv seams = more vert splits — if you don't know what I'm talking about read the 'you're making me hard' sticky in tech talk) and more importantly leads to less interesting textures because you can't have too much detail around mirrored seams, otherwise you get the butterfly effect which is super noticeable.

    Those two tutorials I linked are game-art tutorials which for memory show pretty much the whole process, from high to low to bakes to texturing.
  • Thane-
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    Thane- polycounter lvl 3
    On simple objects im pretty much good on almost the entire UV process, including render settings. Its certain other technical unknowns that make me wonder about certain things and very unsure what i can and can not do that the tutorials i've watched didn't cover. I will check out those other links to (i already did btw, but i probably forgot most of it!).

    Those videos aren't much help IMO. The maker of the gun video won't use any symmetry at all because its intended for the Fallout 3 Vegas Engine and the knife tutorial doesn't use it either, i think because he ends up with text, which im guessing wouldn't look right mirrored.
  • JEmerson
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    JEmerson polycounter lvl 7
    Unwrapping and then instancing the geometry is OK in most instances. New engine changes in Unreal Engine 4, and possibly others (I don't know about others) requires completely unique UV's for all parts of the mesh to properly calculate light maps on the 2nd channel of the uv map (not the first). What does this mean for you? You can either

    A) Unwrap one piece of mesh and instance it, go into the UV map and offset the instanced pieces of geometry by 1, and then in the second channel of the UV map (the second half being done in-engine most likely) completely separate all of the mesh pieces so that all pieces have unique space for light map bakes.

    Advantage: Fewer UV islands reduces the vertice splits, thereby reducing the draw calls (I'm not certain if this is true of instanced geometry though)

    Disadvantage: Extra work once in engine depending on your engine choice

    OR

    B) Just unwrap with completely unique UV islands for all pieces of the mesh, regardless whether it is a repeating piece or not.

    Advantage: Less hassle implementing in-engine depending on choice

    Disadvantage: More UV islands to worry about and increased vertice splitting resulting in longer draw call times.

    As far as your modeling process goes, using instances and mirrors are OK if, at the end of it, you collapse your modifier stack (save 1 version of the file with all modifiers prior to the collapse and 1 version after the collapse) and weld vertices as necessary to further reduce the vertices showing and splitting in the UV map to achieve smaller draw call time.

    *If there is any bad information in here, please correct me but this is my current understanding of the processes*
  • Thane-
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    Thane- polycounter lvl 3
    Lots of info here for people who inevitably run into this thread: http://wiki.polycount.com/wiki/NormalMap#TSNM

    Pretty much answered all of my questions and right on Polycount too.

    Thanks to Sigmfie and Bek for the help too!
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