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Problems with fbx export

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  • Laila Shahzad

    Hi,

    Thanks for posting! Despite the prompt, no smoothing applied to the meshes is lost during the export. It is just that the "Smoothing Groups" information is not embedded within the FBX files that are imported. 

    Now, even though this warning has never caused any hindrance in the usage of the exported asset in any way, still, it begs the question as to what this error means and why is it received. 

    - Is it caused by the Unreal Editor? 
    - Is it due to the MS Plugin? 
    - Is it due to the exported asset? 


    Identifying the Cause.



    The cause is not the Unreal Engine. The Editor just receives the data from Bridge. Since 3D content is being exported hence the UE4 FBX Importer is taken into account by the MS Plugin at the time of export. The MS Plugin feeds all the information to the FBX Importer to present it for display in the Project. 

    Then, is it the MS Plugin causing the issue here; sending no Smoothing-Groups information? 
    No, it is not. The MS Plugin is just a carrier. It extracts the information and passes on to the UE4 FBX Import.  

    Then, is it from where the MS Plugin extracts the information from that's causing the issue here? Yes, it is.
    The FBX information is received from the FBX files within the Asset Directory. It is those FBX files that do not contain the Smoothing Group Information.  


    Comprehending the Cause.



    There are a number of ways to incorporate smoothness in a mesh. Some are generic methods available to most 3D tools. Others are specific to certain 3D tools. 
    Smoothing Groups is one of the generic methods of incorporating smoothness available in most 3D tools. Our 3D artists utilize that process to refine the mesh display.  

    For example, our Rock Cliff 3D asset has been refined to appear smoother. 
    Originally, one could distinguish between every (polygon) face along the surface. Then the mesh is refined through Smoothing Groups to appear smoother.


    Showing the process in 3ds Max, the rough mesh on the left above corresponds to the Smoothing-Groups set on the left below. Similarly, the smooth mesh on the right above corresponds to the Smoothing-Groups set on the right below. 

    Notice that no groups have been selected for (any of the faces of) the rough mesh and group 01 has been selected for all the faces of the smooth mesh. 



    For a detailed understanding of Smoothing Groups, you may refer to the link given below. Reading it with the information stated above will help you understand the concept in a better way. 
    https://knowledge.autodesk.com/support/3ds-max/learn-explore/caas/CloudHelp/cloudhelp/2018/ENU/3DSMax-Modeling/files/GUID-1DB2E3C2-CE68-4AF7-899E-01B90F7EB320-htm.html


    The Reason



    Now the question is; if Smoothing-Groups have been applied/incorporated to the FBX files of Quixel 3D assets, then why do they give off such a warning at export to UE4?

    We have incorporated smoothness via the Smoothing-Groups to our FBX objects, but we have not saved/exported them with their Smoothing-Groups information.
    Whenever a mesh is generated and smoothness is applied to it via Smoothing-Groups and then it is attempted to be exported/saved, that particular tool in use inquires about the export information to be saved within.

    With respect to the case mentioned above, 3ds Max is going to show the following export dialog. In the same way, our artists (whichever tool they have used) faced a similar export dialog as well. Within this export dialog, the option for including Smoothing-Groups was not enabled (just as highlighted below). That is the reason when our FBX files are exported from Bridge to UE4, the Editor prompts a warning that no Smoothing-Group information was found.  





    As stated earlier, leaving the Smoothing-Groups out of the FBX file does not mean that it takes away the smoothness applied to it. It is just that the settings are no longer embedded in the FBX file. Therefore, whenever that FBX file will be opened in a 3D tool, that tool (although will show smoothness in the mesh) but will not be able to display which smoothing-groups made it happen.

    Although it can be ignored since it has no impact on the actual appearance or utilization of the mesh. Having said that, it is a bother to deal with it every time. I shall definitely convey the query to the content team to address this issue and incorporate smoothing-groups information permanently to all future assets (and if possible to the previous ones as well).

    Let us know in case of further assistance required! 

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