Question about continuous meshes for low poly bakes.

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Hayden Zammit polycounter lvl 9
Hey all. I had a question that has been bothering me lately about low poly modeling.

I was told by someone on here in a thread that when they're doing their high poly models, they'll go ahead and use as many intersecting pieces of geometry as needed, but when they do the low poly they'll try and have as much of it welded together as possible.

I was hoping someone could tell me why people do this? What is the benefit?

In the following pic, I'd normally separate out each of those different colored sections as their own mesh, as that's how the high poly was.

YqGVqKG.png

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  • EarthQuake
    That someone was probably me(if not I've said the same/similar things many times).

    Main benefits:
    A. Better uv usage. You waste less space having to uv parts of the mesh that are partially/completely occluded, and you can have more continuous uv layouts which are easier to paint on(less uv islands).
    B. The less unique mesh chunks you have, the easier your bakes are to set up. The less little separate mesh chunks you have, the less you'll worry about intersecting issues etc. Generally anything that doesn't move/animate or have complex overlap gets merged in my low meshes.
    C. Spiting your lowpoly into lots of mesh chunks means more aliasing. Every edge that isn't merged between two mesh chunks is an edge that will alias and look bad in game.

    Some reasons not to merge stuff:
    A. It can cause some more extreme ray direction errors when you bake, that you may have to use a little more geometry to fix. Though here usually a few well placed verts will fix the issue, however, you may need a full extra edge ring in some cases.
    B. It can use up a bit more geometry, so if triangle counts are very very low it may not be a good idea.

    In addition to merging a lot of my lowpoly shapes together, I give a lot of thought and attention to exactly how my highpoly shapes line up. If you're sloppy here, and have a bunch of slight differences in how all your various pieces come together in your highpoly, you can end up with a mess in your low when you merge it all together(or very poor uv usage if you don't merge), with lots of thin little annoying strips to make up the small differences between the various shapes. so you really need to model your highpoly with specific lowpoly topology in mind. I rarely ever model a high poly object that I do not completely understand how the lowpoly will look, and have a rough idea of the geometry/polygon usage it will take to do it that way. Being careless here can cost a lot in terms of geometry count.

    For reference, here is a mesh that is one continuous mesh chunk for the majority of the asset, separate chunks are used for items that will animate, be removed, and for the attachment rails at client request(to save triangles).
    3PointStudios_Brink_Maya_ar02_04.jpg

    And here is what the high wires look like, how the low and high are constructed should have very little bearing on one another.
    ar02wiresbig.jpg

    If I split up my low everywhere I split my high here, even for just the main segments, it would be massively wasteful.
  • Hayden Zammit
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    Hayden Zammit polycounter lvl 9
    Thanks Earthquake. Yeah it was you, now that I remember.


    Thanks for the awesome explanation and the info. I was already trying to keep as much of it merged as possible for the current weapon I'm working on. Glad to know it is a good approach.

    Was a little worried about the extra tris it costs, but I suppose that matters less and less these days.

    That gun looks sweet too. The bake looks awesome.
  • Hayden Zammit
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    Hayden Zammit polycounter lvl 9
    EarthQuake. I've got a quick question about that example bake you posted that I was hoping you could answer.

    1GujbLZ.png

    With things like that round bit I've pointed to, how did you get that to bake correctly? I recognize this gun from the Brink art dump and I read in that thread that you guys baked in maya.

    I'm having a problem with baking a similar piece, as you can see in the next pic. Only way I know to fix it is to use hard edges, which I don't particularly want to, or to change the geo so that there is a vert right in the middle of that round bit. There's no vert in the middle of your bake so I was wondering how you pulled it off.

    yFtpUQZ.png
  • EarthQuake
    Cut in one single vert right in the middle of that shape, the issue is that the mesh normals are point off in some odd direction so you get the skewing there. Post a wireframe overlay shot if you want a quick paintover.

    I didn't get that issue because there are a bunch of supporting edges cut in around that area and the mesh normals are very flat there.
  • ZacD
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    ZacD interpolator
    Also handplane does a awesome job as fixing project distortions without adding to the polycount, add some extra verts, bake a object space normal map, remove verts, generate a tagent space normal map with the reduced low poly and the object space normal map, done. Fixed projection, no extra geometry, quick and simple.
  • EarthQuake
    Yeah, though if you're only fixing a couple spots with a few extra tris, I wouldn't bother with the 2 mesh thing, as you've gotta redo that if you need to make changes and re-bake.

    If you're talking hundreds or 1000s of tris just to fix projection errors, or you have really strict poly budgets, its a nice trick.
  • Hayden Zammit
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    Hayden Zammit polycounter lvl 9
    EARTHQUAKE - Thanks for all the help.

    I know having a vert right in the middle will fix it, I just couldn't figure out how you were pulling it off.

    Here's how the geometry looks.
    nocftSi.png



    3cT8iGW.png

    ZACD - I'd never even heard of Handplane. I always thought all the projection errors I get when I take models baked in maya over to marmoset were just due to bad modeling on my part. Probably still is, heh, but I can't wait to try that program out.
  • fatihG_
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    fatihG_ polycounter lvl 10
    You are viewing face normals here, which as far as I know can only point in 2 directions, inwards and outwards.
    What you need to be checking is vertex normals. Once you do, you'll probably find that the vertex normals aren't perpendicular to the faces.

    What you could do, is either adjust the vertex normals manually, or set up a cage so the rays in that particular area move along the faces normals.
  • EarthQuake
    try this: verts.jpg

    bbox: editing the cage/envelope in Maya only affects ray distance, not direction(like in max).
  • EarthQuake
    ZACD - I'd never even heard of Handplane. I always thought all the projection errors I get when I take models baked in maya over to marmoset were just due to bad modeling on my part.

    Basically yes, bad modeling.
    Probably still is, heh, but I can't wait to try that program out.
    Handplane in itself won't fix your issues. Though it will allow you to create a copy of your mesh, cut in a bunch of supporting loops to fix ray errors, bake an object space map(in your baking app of choice) and then you can transfer that object space map down to the original mesh and output a tangent space map, so you'll save on your geometry count if you need to add a lot of supporting geometry to correct your bake.

    The basic workflow is is described here: http://www.polycount.com/forum/showpost.php?p=817681&postcount=91 though I was using straight up object space maps at the time, so you'll do this + convert in handplane. You don't need to read that whole post, just the stuff on creating a duplicate mesh with extra edges cut in to correct ray projection errors. This post is really old and probably full of dumb advice, so read it at your own risk.

    If you just have one or two areas that are giving you issues, its only a few extra verts or a dozen tris to fix it most likely, so its easier to just cut them in and leave them there.
  • Hayden Zammit
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    Hayden Zammit polycounter lvl 9
    EARTHQUAKE - Thanks for the link to that thread with that weapon you made. In that, your low poly was separate pieces, right? Was that just the way you used to do your low poly models?
  • EarthQuake
    EARTHQUAKE - Thanks for the link to that thread with that weapon you made. In that, your low poly was separate pieces, right? Was that just the way you used to do your low poly models?

    Yeah that post is like 5 years old and I've changed the way I work a lot now. That was just how I did it back then, its sort of embarassing to look at now. :poly124:
  • Hayden Zammit
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    Hayden Zammit polycounter lvl 9
    Yeah that post is like 5 years old and I've changed the way I work a lot now. That was just how I did it back then, its sort of embarassing to look at now. :poly124:

    And embarrassing for me is that that is how I do things now. Reading through that thread, its exactly like how I thought things were supposed to be done.

    Building everything as one mesh is a bit of a pain, but I can see the benefits.
  • SuperFranky
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    SuperFranky polycounter lvl 6
    again im so confuesed does the triangles good for engines like marmoset tool bag or rectangles or polygons or quads or what ? some people says triangles are bad in rendering !
    i just wanted to know? thank you ....
    Different engines triangulate meshes differently. So it's a good idea to triangulate your low poly mesh before doing bakes so the shading stays consistent across every application.
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