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Revit > Max > UE4 Strange UV issue across entire scene (complex problem) 4.19

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    Revit > Max > UE4 Strange UV issue across entire scene (complex problem) 4.19

    Hey guys,

    I'm bringing a Revit model of a building interior into Max using link FBX, then Datasmithing it to UE4 in the standard way. My materials show up correctly in Revit, show up correctly in Max, show up correctly in UE4. Just to confirm, materials are set and sized correctly in Revit using real world values (a 4 inch brick is set to 4 inches).

    I'm attempting to set up the Master Material > Material Instance workflow as advised at Unreal Academy and in Tom Shannon's book. I understand the benefits of this so I attempted to re-build two of our materials this way. Worked great except for a major UV issue.

    The issue is essentially some of my materials in UE4 (those brought in by Datasmith) have arbitrary UV scaling, and some do not (see attached images). So when I build my new materials using the SAME texture image in UE4, the scaling will be correct sometimes and other times be completely off. The main one I'm testing was off by a factor of 8 (so I solved by scaling my material by .125) so I feel like this very specific value is there for a reason...

    This is making the material re-building process overly complicated and confusing since some textures might need to get scaled, some don't, and no rhyme or reason I can see for the difference. Also in the future if some behind-the-scene arbitrary scaling is needed, can it be done to UV's rather than in the material?

    Also, when opening up the Datasmith file in Notepad I can see this in the code, and I suspect this is part of the issue. (notice the .125 values again?)

    <Material name="TestMaterial">
    <Shader name="TestMaterial">
    <Diffuse tex="CT-89_2_2_Tex" coordinate="0" sx="0.125" sy="0.125" ox="0.0" oy="-0.125" rot="-0.000083" mul="1.0" channel="0" inv="0" cropped="0"/>
    Last edited by PSVISUALS; 06-14-2018, 11:32 AM.

    pfbreton might know what is going on.

    Report Unreal Studio bugs here: https://unrealstudiohelp.epicgames.c...I-report-a-bug

    You might want to test with 4.20 to see if we solved this already.
    Sr. Product Manager
    Epic Games


      I'm still seeing this even in 4.20. Seems like Datasmith is building in the texture scaling into it's material it creates so it looks fine, then when I build a material without that it's the wrong size until I scale it.

      Still not sure why some materials are being scaled (and at seemingly different values?) and some aren't being scaled and just come in right. I'll report it as a bug for now.

      And I totally get that someday we will just go Revit > UE4 and this won't be an issue, but its nice to understand.
      Last edited by PSVISUALS; 06-16-2018, 01:11 PM.


        Actually this issue is not really coming from Unreal, it's simply how Revit and Max handle real-world map scale, so it won't matter if you're using 4.19 or 4.20.

        These numbers that you saw are not as arbitrary as you might think or if they are, that's only because of real-world texture sizes. So if a brick texture in Revit is 40"x40" in real-world size, in "tiling size", it may read something like 0.01x0.01 (when you uncheck the real-world map scale at the texture level in 3ds Max's Material Editor). A bigger or smaller real-world texture size will give a totally different tiling size, which gives you the impression of arbitrary numbers.

        Like I said, it's just how real-world mapping works in Revit and Max and if you were to apply an Unwrap UV modifier to any object coming from Revit such as a wall, you'll see that the coordinates go way beyond the 1:1 packing square, which is workable but not necessarily clean.

        I agree with you though that it would be so much easier if the default tiling was always 1x1. This could be arguably achieved and even possibly automated with the help of a UVW XForm modifier. It's something i will look into.

        hope this helps,

        Amer Yassine
        Unreal Studio, Montreal


          Thanks for explaining Amer, that's a big help!
          Sr. Product Manager
          Epic Games