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Maya-Arnold 5 Strange Artifact with Bump

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  • Maya-Arnold 5 Strange Artifact with Bump

    I exported a tree in FBX format and imported it in to maya (through the SpeedTree plugin) choosing the "SpeedTree for Arnold 5" option.
    But when I try to render it with Arnold, If I leave the bump map, as it is in the shading network, I get some strange results:
    - strong borders on the joints between the branches and the trunk
    - too much strong shadows
    - and I visible line separation between the ttwo borders of the texture

    Especially the first problem is for me the most annoyng. If I take off the bump, the problem disappears.
    I took two screenshots, the first one with the bump map (where you can see the issue) and the second one without it.

    Is there any way to solve these starnge problems, especially the first one?


    Click image for larger version

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  • #2
    Hello, It looks like you have some lighting edits that you may need to make over the branch generator. The normal map is facing outward on the tree trunk, while the branches might need to be adjusted in the welding.

    I'd start by turning on "View" > "Normals" so you can preview the normal's vertex angle. In the branch generator properties, head to "skin">" blend"> "lighting" and adjust the weld area. You can also adjust over the branch under "skin">"radius">"light seam reduction".

    We're also running some tests to make sure the exports are coming in right- If we find anything we'll let you know!
    Last edited by SarahScruggs; 04-12-2019, 10:00 AM.


    • #3

      After looking into this, it seems that there was no Branch Seam Blending in the Arnold script. This is what is causing that line in your textures where the branch and bark and meeting. We will update the script, but for the moment, I will tell you how to get Branch Seam Blending to work.

      Open the Hypershade in Maya to see your materials and select the Bark material. Add a 'aiUserDataColor' node and type 'blend_ao' in the 'Attribute' section. Blend_ao is actually a texcoord, it just happens to come in as a color. Next, connect the aiUserDataColor's -> 'OutColor R' to the Bark Material 'Opacity' -> Opacity R, G, B. The Red from the aiUserDataColor is blend and will blend the branch seams.

      Here is a screenshot of how the connection should look. Where ever you had Branch Seam Blending in the modeler is where you will want to add this. So if you have two bark materials where the blending is happening, then I would apply this node to both materials.

      Click image for larger version  Name:	Arnold_blend.JPG Views:	0 Size:	77.6 KB ID:	6658
      Hope this helps!
      Last edited by SoniaPiasecki; 04-12-2019, 10:52 AM.


      • #4
        thanks for your early reply. I tried both of yours suggestions but the problem is still there.

        Idjusting the "skin">" blend"> "lighting", can help a bit in certain situations, but the central
        issue is that there is no actual texture blending, even when there is no bump mapping.
        You an see it, on the imported tree in maya, looking closely to the joint point. That is quite different
        from what you can see inside SpeedTree Modeler, where the blending works very well.

        Of course, when a bump map is used the result is much worse.

        I trid to fix this as you, Sonia, suggeted, using aiUserDataColor, and so on, but that didn't work.
        The result was the same, as I didn't do anything.

        So I think here the problem is to find a way to make a real blending work....