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Thread: Linking Revit to 3DS via RVT/FBX - ISSUES - 2018 and others

  1. #1
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    Exclamation Linking Revit to 3DS via RVT/FBX - ISSUES - 2018 and others

    Hello,
    I would like to open this topic as a continuation of the following thread, just updated to current situation:
    https://www.revitforum.org/rendering...dsmax2016.html

    The question is: do you find difficulties with linking Revit files in 3ds Max and further workflow, using either RVT or FBX, in any of recent Autodesk versions?

    By far, I have tried different configuration (mostly on 2018) to achieve reliable linking in any of the extension, but I found many issues which stopped me from doing the project or made it really hard. These are:


    Linking with RVT file:

    issues:
    • "Bad faces" - improperly displayed in viewport and rendered faces, usually darker than they should be, with artifacts. After tests and reading many posts found out this may be all connected with normals of imported mesh, which might be set wrongly on mirrored(!) Revit objects or are not read by 3ds properly.
    • ALSO nesting Revit model in different Revit project and multiplying its instance with rotation/mirroring results in improper shading in 3ds viewport and render when the host Revit file was linked.

    examples:
    • typical windows mirrored along the wall (at least one of them might have corrupted faces)
    • simple building model nested into site model (RVT into RVT file), then copied with rotation or mirroring (in 3ds copies don't see lighting directions properly, the house which was rotated 180* has shadowed faces in front of the sun)

    workarounds:
    • applying modificator 'Edit normals' with Reset/Break options on every object (this probably changes explicit normals to specified; cons: each time a new material object comes from Revit during relink, you must/should find it and apply modificator)

    solution:
    ?

    Linking with FBX file:

    issues:
    • Although size of geometry is good, material domain is broken (overcalled), despite same metric(!) units in Revit, 3ds and Windows. As we can read in many sources, FBX file is natively converted to feets/inches, but this does not explain why conversion during linking process is corrupted. I am not aware if the problem occurs for users who use imperial units natively. Material domain issue concerns not only materials but scattering objects as well.
    • 3ds cannot relink FBX file from Revit project if the latter contains nested model with more than one instance

    examples:
    • any Revit object with defined size (like floor 10x10m) linked to Revit and covered with simple checker material
    • host Revit file with multiple instances of same house, linked to 3ds and then relinked (result: error and crash of application)

    workarounds:
    • applying 'Mapscaller' modifier to each specific material object resets the domain (must be applied again to any new material objects which comes with relinking)
    • no workaround for multiple instances issue

    solution:
    ?

    This is my experience so far. Neither RVT or FBX linking gives me reliable and painless workflow.
    If you had any of these issues or have a solution please join the conversation.


    Also, these are links to the topics connected with those issues. I put them some print screens showing what is going on.

    "Scale/units issue while exporting Revit to 3DS with FBX"
    https://forums.autodesk.com/t5/fbx-f.../7659583#M9130

    "Re: 3ds MAX/Revit link geometry lighting issue"
    https://forums.autodesk.com/t5/3ds-m...t/true#M149861

    Thanks.
    Last edited by imigas; October 4th, 2018 at 08:18 AM. Reason: additional links

  2. #2
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    I use FBX (instead of RVT linking) for my max workflows. I might link RVT initially, just to see how the scene imports, but it leaves too many things uncontrolled (or controlled automatically) for my tastes.

    I think part of the problem might be that you're trying to link the entire model at once. I've never been a fan of this; it takes too long, complicates material reassignment, and doesn't deal with model changes very efficiently. I use different 3D views to break the model into FBX files, based on a common purpose. For example, I'll configure a "core & shell"view, an "interiors" view, and potentially any site work as a separate view. Anything that I'm going to replace with more sophisticated geometry (lighting, furniture, etc) gets it's own view. The FBX gives me an opportunity to replace repetitive things like lighting and furniture with instances and references (instead of distinct objects), or to set up proxy geometry. Now I can link each FBX into it's own max file, tweak geometry, and assign materials. I then link each max scene into a master file that contains the lighting and cameras (as these should be based on your rendering engine and often require the most frequent tweaking at render time) and render from that scene.

    Some things you NEED to get out of Revit (UVW mapping for example) as it's terribly time consuming to apply UVW maps to each object in the scene. I've only experienced UVW map scaling issues when I forget to set the FBX import units correctly (needs to be feet). Applying a UVW modifier to everything and scaling down to 1/12th worked for me in that case.

    Another advantage of FBX is that it doesn't really matter WHAT the file comes from (theoretically you could mix revit versions by exporting both to FBX). You don't have to export from a massively linked model, you can export from each individual link (coordinates permitting). The max scene also doesn't automatically reflect any changes, since you're working from exported FBX files and not the RVT.

    You've got to think about the purpose, goal, and target audience of each shot you want to render, and prepare accordingly before you get to max.

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