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Problem with Bump Maps in Iray

ToyenToyen Posts: 1,906
in Daz Studio Discussion

Hey there guys!

I am having a problem with bump maps in Iray.

After plugging in the bump map and setting it to 1.0, I get these weird jagged shadows showing up.

I have had similar problem some time ago with normal maps doing this but it turned out there was something wrong with my normal map, however here I see nothing wrong with the bump map I am using.

A regular black and white image of the fabric.

Has anyone else experienced this? Let me know!

bumpproblem.png
1080 x 868 - 741K

Comments

  • ToborTobor Posts: 2,300

    The old shadow terminator artifact. Try increasing the mesh resolution of the fabric. 

  • ToyenToyen Posts: 1,906

    It does look better when I Subd the mesh, but you can see it is still there if you look closely.

    Is there really no other way to get rid of this besides making the geometry ridiculously high poly?

     

     

  • mjc1016mjc1016 Posts: 15,001
    Toyen said:

    It does look better when I Subd the mesh, but you can see it is still there if you look closely.

    Is there really no other way to get rid of this besides making the geometry ridiculously high poly?

     

     

    Upping the mesh geometry is problably the easiest way...but you can try normal maps, instead of bump...even if they are converted from bumps.

    Now the question I have, are you doing a render at a large enough resolution or close enough that the bump map (which I am assuming is a cloth weave) is really going to be noticeable...because the shadow disruption definitely is noticeable and if the shot isn't going to show that detail, the quickest/best solution...eliminate the bump.

  • ToyenToyen Posts: 1,906

    I am already using a normal map for a different effect.

    Displacement map does not give me the desired results at all.

    I checked out bump maps on other things such as Daz characters. They have white background but other than that, there isnt anything special about that that would make sure the shadow issue does not happen.

    So I changed my background to white but that didn' t do the trick obviously : D

    I' d love to get to the bottom of this.

  • mjc1016mjc1016 Posts: 15,001

    Click on the map, in the Surface tab...and there should be an Image Editor choice in that drop down.  Click it and set it to 1.0 for Gamma...that will tell Studio to leave it alone and not guess what correction, if any should be applied to it.  See if that helps.

    And for displacement, you need higher subdivision, too...

  • ToborTobor Posts: 2,300
    Toyen said:

    I' d love to get to the bottom of this.

    Well, the bottom of it is an inescapable limitation of many renderers that work like Iray. By googling 'shadow terminator artifact' you can find people on various forums and blogs talking about it. Here are a couple of examples, with some suggested work-arounds, including one or two you've tried:

    http://mayastation.typepad.com/maya-station/2009/11/the-terminator-effect-shadow-artifacts.html

    http://blog.irayrender.com/post/29042276644/shadow-acne-and-the-shadow-terminator

     

  • ToyenToyen Posts: 1,906

    Thanks for the suggestion but the gamma correction did not work.

    I really wonder why is it acting up like this. All the bump maps on items like hair and character skin I have in my library are working properly.... : / And they seem to be regular black and white bump maps, nothing special about them.

    And thanks for the links Tobor, I have already seen the article about this problem.

    The displacement cant really be used here since it distorts the geometry severly.

     

  • mjc1016mjc1016 Posts: 15,001
    Toyen said:
     

    The displacement cant really be used here since it distorts the geometry severly.

     

    Then the geometry isn't fine enough...displacement in Iray needs a much finer 'dicing' than it does in 3DL (3DL does it at render time,  on the fly).   If there were enough detail, then there would be very little difference in look between the bump and the displacement...

  • millighostmillighost Posts: 261
    Toyen said:

    I am already using a normal map for a different effect.

    You put a bump and a normal map in at the same time? Very bad idea unless you know what you are doing (i.e. you have baked your bump map against the distorded normal).  

    The displacement cant really be used here since it distorts the geometry severly.

    Bump maps give the same shading as a displacement map (only without the geometry change), so if the displacement does not work, bump likely will not be great either.

  • ToyenToyen Posts: 1,906

    I am using normal map to create folds in the fabric that I have sculpted on the high res version of that mesh and the bump map was to be used to add more detail to the texture of the fabric.

    Actually the bump is giving me the results I would like minus the shadow artifacts, while displacement does this:

     

    image

    I can achieve similar effect of the bump map by just using diffuse map alone so now, I just really wanna figure out why it doesnt work : D

    displacement.png
    1053 x 858 - 786K
  • mjc1016mjc1016 Posts: 15,001

    Can you post a wireframe screenshot? 

  • ToyenToyen Posts: 1,906

    Sure. 

     

    wireframe.png
    523 x 853 - 175K
  • ToborTobor Posts: 2,300

    You don't have to dial up a high displacement. You need to increase the geometry. The first link in my post above has the explanation why this happens, so I'm not sure why you're still mystified by it.

  • ToyenToyen Posts: 1,906

    The picture of the displacement I have posted was with the geometry already increased.  I know how it works : )

  • mjc1016mjc1016 Posts: 15,001

    If you take a close look at the wireframe compared to the Bump 1.0 image you'll notice that the 'jaggedness' of the shadow is almost perfectly matching the size of the polys...easiest to see at the almost square shadow on the knee.

    Polygons are 'cheaper' than image maps...less memory is used for more polys than is used for more detailed maps...(a typical 4k image map is going to eat around 48 MB of memory...you can have a rather detailed/pretty high poly mesh in that same 48 MB).  And actual mesh geomery has a bit less overhead than cranking up the subdivision level in Studio. 

    So, increase the geometry some...I would probably divide the mesh in my modeller, before bringing it into Studio, at least 1 time.

  • ToborTobor Posts: 2,300
    Toyen said:

    The picture of the displacement I have posted was with the geometry already increased.  I know how it works : )

    Then you need to increase it more. This problem can even appear on G2F with high resolution mesh, so just upping it one or even two levels may not be enough. The combination of elements, including lighting and shadow hardness, makes it more apparent, and you're hitting a "perfect storm" of that combination.

  • ToyenToyen Posts: 1,906

    I'll probably just use diffuse map. The detail is so small that I don' t think it is worth those thousands of extra polygons if I were to subdivide the mesh in my modeler.

    I' d still love to know why some bump maps work and some dont though : D But I guess that is just hit or miss with the bump maps.

    Thanks for everybody' s suggestions : )

  • mjc1016mjc1016 Posts: 15,001

    I think the more 'regular'/uniform the pattern is the more likely to cause problems.

  • ToborTobor Posts: 2,300

    Apparently there's a new feature in the beta of D|S 4.9, just out, for reducing the effects of shadow terminator ugliness caused by low tessellation such as this. If you're the pioneering type, you might want to try it out to see if it makes a difference.

  • omnifreakeromnifreaker Posts: 71
    Tobor said:

    Apparently there's a new feature in the beta of D|S 4.9, just out, for reducing the effects of shadow terminator ugliness caused by low tessellation such as this. If you're the pioneering type, you might want to try it out to see if it makes a difference.

    What is this "new feature" pray tell?  The problem seems to be that once you use bump/normal maps, the geometric normal is totally overriden.  I was hoping bump would be more of an addative rather than replace effect.  

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