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Zbrush - Zremesher won't preserve polycount

sin10001
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sin10001 null
Hi all!

I'm trying to Zremesh while preserving my polycount, but it always reduces it to 1/4 etc even if I have "same" selected. Any ideas?
I think I've tried most combinations of settings in the Geometry tool > Zremesher, and "freeze boarder" is the only one that seems to keep the polycount ... but it also keeps the triangles I'm trying to get rid of ...

Put another way, anyone have good solutions for perfectly quadrifying a high-poly model so that I can "recreate subD" in zbrush?

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  • cryrid
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    cryrid interpolator
    I don't think zremesher is meant to output exact numbers. It's looking to automatically retopologize the entire model based on the flow of the surface, and the user controls are more of a guideline for it to take into consideration when it does so. 

    I also don't think you'll find any automatic retopology solution that will spit out topology that is compatible with Subdivision Reconstruction. Reconstruction is pretty specific and only works if the current topology can be created through subdivision. This means the retopology would have  had to create a lower resolution, then subdivide itself while discarding the topology you want. 

    It sounds like you just want to preserve the existing model, but untriangulate it? If so, try Tool: Geometry: (Modify Topology) MergeTris

  • sin10001
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    sin10001 null
    Thank you for the reply cryrid!!
    I really appreciate it. 

    If I may, a follow-up: is there any easy way to create uv's for a low-poly version of my current model? That's essentially where I'm trying to go with this ...
    The workflow I know I might have to do is
    1. duplicate the high-poly and zremesh
    2. subdivide and project
    3. fix anomalies (the thing I really loathe) ... fingers and toes, overlapping geometry (no idea how to fix that) and other reasons I can't figure out cause vertexes to get shot out into space after projection. 

    Any further thoughts or suggestions would be greatly appreciated!
  • cryrid
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    cryrid interpolator
    I'm always a fan of baking your maps in another program, like xnormal. This way you don't have to worry about subdividing and projecting the details back inside of zbrush, and fixing the errors that can occur as a result. You'll also get more control over the normal maps this way.  
  • sin10001
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    sin10001 null
    Thanks for the replies cryrid - I really really appreciate it. Honestly, I'm slow to dealing with it bc I'm dreading the process. 
    If I may, here's another follow-up: why wouldn't I need to subdivide, even if I baked maps in another program? 

    Essentially, I don't truly get how high-poly detail can be transferred to a low poly model - in a magical world, I'd just create maps for the high-poly one, even though it's verts are in different places than the alternate, low-poly one I have (this was my first model, & I ultimately didn't follow a linear workflow), and then be able to apply them to that other, lower-poly model ... but that's impossible/ineffective, right?  Cuz the verts are in different places?

    Let me also state my understanding so that you can clarify (if you'd be so kind): vert position is key, yes? If I start on a low-poly model and keep sculpting on subsequent, higher-subd lvls, the vert positions of the highest poly model will be rooted in the original/parent verts. Any maps made will have the original verts in common, effectively. In addition, all rendering software subdivides the same exact way, so one can use deformation maps in anticipation and reliance on this fact ...... maybe?
  • cryrid
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    cryrid interpolator
    Long story short, when you create maps in a program like Xnormal, only the lowpoly mesh needs UV coordinates. The highpoly model doesn't need UVs, or matching topology / vertices; it's surface only needs to occupy the same general space as the lowpoly model.  

    The baking tool
     will start a certain distance out from the lowpoly model, and then casts rays inwards towards the high-poly sculpt. When a ray intersects the sculpt, it records the surface detail and saves that into a texture map using the lowpoly's UVs. 

    This method frees things up on since you don't have to worry about matching topology and vertices between the sculpt and the game mesh (good topology for sculpting isn't always good topology for games, and vice versa). You can create your highpoly sculpt however you want (mash shapes together, dynamesh then, etc), and then once you're happy with the result you can retopologize it to create the lowpoly game asset. 
  • sin10001
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    sin10001 null
    You rock - this is really helpful

    The reason I keep going on about "how do displacement maps work" is because of all the artifacts I get from projecting in Zbrush. I can't think of why a low-poly w/ different topology wouldn't experience the same artifacts, unless render engines just ignore (instead of trying to force) unaccounted-for verts into places. 

    I've done a bunch of reading up on baking displacement, but if you're willing to explain how it works that'd be a super-duper bonus!
  • EosOfOrcus
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    EosOfOrcus polycounter lvl 4
    sin10001 said:
    Hi all!

    I'm trying to Zremesh while preserving my polycount, but it always reduces it to 1/4 etc even if I have "same" selected. Any ideas?
    I think I've tried most combinations of settings in the Geometry tool > Zremesher, and "freeze boarder" is the only one that seems to keep the polycount ... but it also keeps the triangles I'm trying to get rid of ...

    Put another way, anyone have good solutions for perfectly quadrifying a high-poly model so that I can "recreate subD" in zbrush?

      Hey man. When you use Zremesher. Try to turn off adaptive or reducing the adaptive Strength. When you have adaptive turned on it will increase/reduce the polycount and also it will create extra trangles or poles to closely match the shape of your mesh.

    Also Zremesher doesn't really try to match your polycount but you can try to get close to your polycount if you increase the number on the target polygons count slider. Then sliders number represents thousands so if you have 5 then it's 5000 polys
  • sin10001
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    sin10001 null
    Hey Eos,
    Thanks for the note - I knew most of it, but the reminder about triangle creation was just as helpful! 
    I'm still trying to figure out how to get past this problem. I haven't yet tried baking displacement maps in another program, so I guess I'll have to, but I'm also wondering whether welding meshes together deletes UVs? If not, I guess I can just weld on the parts after I copy my original model at whatever level of detail I want ...

    If you're available for a couple of PM questions, that would be great =D

    Either way, cheers!
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