Poor quality render on Unreal Engine with Object (.obj) from 3d Max

[Anonymous]

Hi folks,

We are doing a university project that involves using some Lego 3d models on Unreal Engine. We work with the 3d models in 3d max where they show good rendering quality but when imported to UE they look very bad.

The models come initially from a Lego modeling software LeoCad but since the models look good on 3d max, we believe the problem is in the exporting/importing phase from 3d max to unreal engine. How should the settings be configured to obtain an optimal result?

See some snapshots illustrating the difference in the quality:

The first image corresponds to 3d studio and the second in UE.

We also encountered a few warning messages in the process that can give some hints on what the problem might be:

Export:

Import warning:

"No smoothing group information was found in this FBX scene. Please make sure to enable the "Export Smoothing Groups" option in the FBX Exporter plug-in before exporting the file.

Even for tools that do not support smoothing groups, the FBX Exporter will generate appropriate smoothing data at export-time so that correct vertex normals can be inferred while importing"

but in fact this export option was there.

Thanks for your help!

Eloi and Ernest. Medialogy students at AAU

[lightcube]

NOt really sure but you have the OBJ exporter dialog in the screen shot, not the FBX exporter. Try exporting as FBX and NOT as OBJ.

[PROH]

Yes, as Lightcube say you seem to confuse OBJ and FBX. There are also a couple of other things to note:

1) If you take a look at the "grass" in the Max render, you'll see that the knobs aren't smoothed. Looks like you haven't applied any smoothing groups to the objects.

2) The "rats nest" warning relates to the way the geometry is made, and is likely to come from the original CAD file, since most CAD programs produces geometry in a way, that makes poor meshes.

3) Looking at the UE picture, it's clear that some of the objects are inside out. You can check that in Max by activating "Backface cull" in object properties (select all - right click - select "Object Properties" - check "Backface Cull" - press OK). This way Max will display things the same way as UE (and other game engines) does, and therefore makes it possible for you to spot these problems.

Hope it helps

[Anonymous]

I agree with Proh - your normals are flipped.  In the edit mesh properties, there is a surface properties category where you can flip normals so they are facing the right way.  Make sure you turn on backfacecull like Proh said, otherwise you'll have a hard time telling which faces need to be flipped.

[Anonymous]

Hi, Thanks for your solutions. It seems to point in the right direction but flipping normals while it corrects some surfaces, breaks other ones.

What worked best for us so far is disabling backface culling in Unreal Engine, yet we have been warned about performance issues on doing that.

We'll be very happy to consider better solutions or at least get to know a little bit more on how this could be improved!

BR, Eloi and Ernest

[Anonymous]

We tried FBX as well with the same results. What is the advantage of using FBX compared to OBJ?

Thanks

[lightcube · Accepted solution]

Apply the Normal Modifier to your models, and make sure Unify Normals is ON. If this has no effect, make sure to weld all vertices first.

As for FBX... it is simply more robust and exports more features. Unfortunately, some features are currently broken relating to UV as of last time I exported to FBX.

[Anonymous]

This works very well. Thanks @lightcube 

How about the smoothing issue @PROH pointed out before. Do you know anything about that?

[lightcube]

The fastest fix is to apply a Smooth Modifier and choose Auto option. You may need to manually update the smoothing groups for specific needs. In that case, you should look up smoothing groups in the Max docs.

[Anonymous]

Really nice that did even better!