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Thread: Zbrush Normal Map Generation Problem

  1. #1

    Zbrush Normal Map Generation Problem

    Hello,
    I have a problem with Normal Map Generation in Zbrush.
    This really isn't related with LightWave but I am not familiar with the other forum so please forgive me asking this.

    Here's what I've got. I'm trying to generate normal map.

    The method works----
    1. Import obj.
    2. Store morph and UV Master it.
    3. Sculpt.
    4. Back to stored morph target
    5. Generate normal map.

    The method does not work----
    1. Import obj.
    2. Store morph.
    3. Sculpt.
    4. Back to stored morph target and UV Master it.
    5. Generate normal map.

    UV mapping the object after sculpting makes normal map unusable.
    Is this right? Maybe I should have known before... but I need a confirmation on this.
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  2. #2
    i dont know for sure but it could be because its recreating a normal for all
    pixols/polys since all the pixols/polys are being addressed when UVing
    after sculpting. The program may have to give those pixols/polys some
    value when that workflow is used.

    looks like its scanning the over all shape of the original object
    and then reprojecting the detail into a normal map. could be useful
    Last edited by VonBon; 01-26-2012 at 09:23 AM.

  3. #3
    Goes bump in the night RebelHill's Avatar
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    Ideally, yes you should UV it before going and subdividing and sculpting. Though, and I cant remember for sure (cos i always do it first), maybe if uving after u need to make sure to go back to base mesh level 1 first.
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  4. #4
    Robert Ireland bobakabob's Avatar
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    Are you sure your obj only has one uv map in LW? If so it should be ok. Ensure your obj doesn't have multiple uvs by deleting once in zbrush and starting afresh. ZB can't work with multiple uvs and can scramble maps. Create uvs either automatically with Puv button after polypainting / sculpting or use additional uv plugins. Haven't tried UV master but it looks even better as it creates maps that can be understood by the human eye and embellished in Photoshop. Just be sure to save a copy of your sculpt before applying. Simplify Normal Map generation by using Multi Map Generator plugin -it will export your Uv mesh (at resolution you determine) plus maps into one neat folder. Plus GoZ seems to have accommodated LW for streamlined importing. Read up on Steve Warner's early ZB > LW tut on ZB Central - now a little out of date but full of useful info about the fundamentals and gotchas like not flipping the vertical, which can be corrected in Photoshop. In LW apply subdivision and smoothing and ensure the normal node is plugged in correctly. Check YouTube for a tutorial on LW 11 displacement. Normal maps do work well in LW and give you great renders. PS I never usually bother with Morph targets, could something be going wrong there? PPS Your model looks like it's still in Zbrush, if you're rendering here you don't need a normal map, genuine hi res displacement looks infinitely better.
    Last edited by bobakabob; 01-26-2012 at 04:19 PM.
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  5. #5
    Adapting Artist jasonwestmas's Avatar
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    You can import any UVs by loading in your obj mesh object on top of your Ztool at Sub-D level1. You don't have to save a morph target, just load in your obj file again. Otherwise, just go down to sub-d level 1, import your original obj (cage model) and apply PUV or GUV tiles. Then generate your normal map. . .should work fine.

  6. #6
    Thank you for feedback!

    VonBon,
    yeah it could be useful but I want here is precise control! I want Normal map only to affect where I put some stroke. In this case, four prominent on the head.

    RebelHill,
    Maybe that is the answer. UV it before subdividing.
    But everything else except the order of UV generation is completely identical. The identical base mesh (Stored Morph at SubD level 1), the identical UV layout (generated by UV Master based on Stored Morph at SubD level 1). The identical high res detail. Only the order is different. Ztools are completely the same by the look! You really cannot tell the difference! Only the output is different. This is the confusing part.
    I also consider this. In this particular case, I bring back morph target. So there is no problem UV it first (don't know why though). But if you don't intend to go back to morph target, simply use the level 1 mesh to generate maps, it's better to generate UV after sculpting has done? Since the final level 1 mesh is altered by subdividing and sculpting?

    I kinda hope there's a way since it took a whole day to add detail on the mesh...(not the one I posted)

    bobakabob,
    There's no UV when imported in Zbrush. I only put this model for examination. It's subdivided a couple of time and added some prominent on the front head. LightWave is not problem here. It's entirely about Zbrush. I think you should try UV Master btw. It's really time saver. Although you cannot edit UV layout in Zbrush, It's sufficient for simple work. A couple of click and done!

    jasonwestmas,
    I personally prefer to store in Ztools rather than have an additional file in the folder.

  7. #7
    Adapting Artist jasonwestmas's Avatar
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    Well don't loose that obj file, you may need it incase your UVs or base mesh get screwed. If you post the Ztool I can tell you what is wrong.

  8. #8
    Jason, thanks for offering.
    Hmm maybe the way I work is not right? Please examine the attachment.

    There are four files.

    test.obj and test.mtl is exported from LightWave. It has no UV. I made UV using UV Master in Zbrush from Morph Target State so they are identical.
    test_uv_before_sculpt.ZTL is the one which produce the right normal map from Morph Target. UV was created before subdividing and sculpting.
    test_uv_after_sculpt.ZTL exports strange normal map from Morph Target. UV was created after subdividing and sculpting then went back to level 1 Morph Target. I want this one to generate the right normal map.

    Zbrush is the latest one.


    ---Edit

    Okay, I noticed something strange. Open test_uv_before_sculpt.ZTL and delete UV. Create UV again from Morph Target. This operation alters the mesh! Why does UV creation alter the mesh... But looks like it's the very reason Normal Map is badly affected.
    Last edited by VermilionCat; 01-27-2012 at 10:35 PM.

  9. #9
    Adapting Artist jasonwestmas's Avatar
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    you appear to be using R2b. I'll have to get back to you after I update.

  10. #10
    Thanks, Jason. Yes, I am using R2b.

    1. Import object.
    2. Store Morph
    3. Subdivide couple of times (and take a screenshot)
    4. Back to subd level 1 and switch to the morph target
    5. Create UV
    6. Switch Morph
    7. Go to highest subd level (and take a screenshot)

    Compare the two screenshots. The mesh is altered. This is why I am getting wrong result. Isn't this strange? Or the way I did is wrong?

  11. #11
    Adapting Artist jasonwestmas's Avatar
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    I just followed that precisely in R2 (using PUV tiles) and there was no alteration between the two meshes. Maybe an R2b bug? Did you ask in Zbrush Central?

  12. #12
    Adapting Artist jasonwestmas's Avatar
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    There does appear to be an issue with UV master though. After I cloned my mesh with UV master there was a shift in the highrez at sub-d level 4. I know because the tangent normal map then detected an alteration between the morph target and the subD level 4. Could just be one of those things that aren't perfect.

    Maybe there's a step we are missing. Did you review the old UV master videos?

  13. #13
    I did too using PUV tiles and no, there's no alternation in R2b. I've used UV Master so this must be UV Master problem.

  14. #14
    Ahh. Thank you for further testing.
    Yes, this must be UV Master. I'll check on the web.

  15. #15
    Adapting Artist jasonwestmas's Avatar
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    I haven't used UV master since it came out but I think I recollect you are only supposed to apply UV master to the highest sub-D level. I think the videos explain this? I just did a test and it appears to work fine that way when you create your clone and then copy and paste your UVs to the original mesh on the highest sub-d level.

    Edit: yes I don't see any issues anymore, do the above and see if that works for you.
    Last edited by jasonwestmas; 01-28-2012 at 10:08 AM.

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