BRep to Mesh gave me this. How can I fix it?

[ambiroa]

This is the original work in progress

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I converted with BRep to Mesh, and saved as OBJ. I then UV unwrapped it in 3D Coat, imported into Substance Painter, and this is what it looks like.

I showed this in the Substance Discord channel, was replied that the issues are related to 'smoothing groups'. Because I haven't done any manual smoothing, the only thing I can think off is that during the BRep to Mesh procedure, something went wrong.

1. How to fix this? What steps do I need to follow to get a clean mesh? (I still have the original of course)

2. Is there a better way to get my models out of Fusion, so I can continue my pipeline?

3. I love to hear from others how you take your models from Fusion to other programs.

Thanks.

[PhilProcarioJr]

@ambiroa

This is related to smoothing groups. You need to open the .obj file in a poly modeling app and apply smoothing groups.

This has nothing to do with your workflow in Fusion or Fusions export of the mesh. (Sure the Fusion dev team could add the ability to export smoothing groups but they haven't so you have to do it.)

For me I export my meshes and open in Maya, select the meshes and select the smoothing angle and apply then save. Perform my UV layouts in either Maya or Zbrush and save.

Open in substance designer and generate needed maps, then start working on my materials.

At some point I want to add this to the training kit I am working on...

[ambiroa]

Hi Phil,

Thank you for the rapid response.

I'm a 3D beginner, so to make sure I understand this properly, what exactly does 'smoothing groups' do? In case it's called differently, then at least I know what to search for. Also, do you have tips on what settings I need to type in during that BRep to Mesh dialog? I don't really understand what the settings do, so I selected High, waited til Fusion stopped freezing, and that gave me a 200k poly OBJ. Is this even the correct setting?

[PhilProcarioJr]

@ambiroa

As to smoothing and what it is, look here at the Blender Manual. You can do the smoothing groups in Blender and it is free.

https://docs.blender.org/manual/en/dev/modeling/meshes/editing/smoothing.html

http://wiki.polycount.com/wiki/Smoothing_Groups

What settings you use depend on how accurate you want your mesh to be. Before I can really help you I need to know exactly what your trying to do with the conversion...IE are you going to put this in a game engine, are you trying to do production renders.....?

Also depending on how much your wanting your meshes to match your CAD models you might need to dive into Normal maps...this is actually a very complicated subject, but I will take the trip and help you out once I have more info.

[ambiroa]

Ultimately, the plan is to put this into Unreal Engine, and export both a still image and a short movie (the valve will be part of more meshes including pipes on the wall, and a door at the end of a small corridor; I'm trying to recreate a scene from the game DOOM 2016).

So Ideally, I will have a high quality textured model at the end, which I can also render in IRay for additional presentation visuals. Obviously I need to retopo for a lowpoly in case I need it.

Basically, I just want to take my model out of Fusion, nothing more nothing less. Parametric modeling seems to connect with me and Fusion is a wonderful tool, but in terms of taking it through a non-cad/cam pipeline, it comes short, I mean, it could all be much more easier. Until that happens, if that happens, I just need to find a way to keep the model exactly the way I want it, and without errors.

As mentioned, I'm a beginner. But when I model in a polygon modeler without any extra steps, uv it, it looks clean in substance. But a model out of fusion, without additional steps, creates these errors that requires me to do the smoothing groups step, ... why? Why does it give me those errors in the first place?

[PhilProcarioJr]

@ambiroa

"But a model out of fusion, without additional steps, creates these errors that requires me to do the smoothing groups step, ... why? Why does it give me those errors in the first place?"

Simply put Fusion wasn't meant to be used the way your using it. It was meant to be a CAD app for the manufacturing of real parts, not realtime display in a game engine. So it's not that Fusion couldn't be coded to use, create and export smoothing groups...it's that no one has asked for it. In order for the dev team to implement it you would need to add it to the idea station and enough people would need to vote for it.

I did read the other day though that Autodesk is working on allowing the Stingray game engine to render Fusion models in realtime but until that is done we will have to prep the models manually. The reason you didn't have to create the smoothing groups when you were poly modeling is most polygon modelers add smoothing based on your surfaces so a lot of the time you don't have to do it. In this case though you have no choice.

So based on what your doing you have a lot to figure out, for instance how much will be in your scene for performance reasons. But first I would tackle the smoothing groups problem.

What Poly modeling app do you use?

[ambiroa]

I use Rocket3F. You probably never heard of it, it's a brand new pure modeler targeted to concept artists, it has a subdivision action which is called 'Subdivide' in the program, at from the looks of it, I can use that for a bit of smoothing. Other than that, I have Modo installed.

What I noticed is that this issue occur with holes, and that the Fusion export added a lot of extra tris to maintain the hole. I also saw the those lines were directly connected with the edge loop of the hole itself, so I guess one of the things I should try is isolating that area a bit by adding a ring loop around the edge, which I believe is a common thing to do in polygonal modeling holes. It also occurs on top of my valve, where in the original model, I placed a cilinder into the valve top, and during the BRep process it merged together. So again something related to round small shapes.

Finally, I noticed that importing the obj, it placed it sort of in the same world position I have it in Fusion, so my guess is, if I NOT merge all my bodies, instead exporting them all separately, and import them all in the same scene, they should be all alligned perfectly, maybe this could decrease the chance of errors?

[PhilProcarioJr]

@ambiroa

Look at the hard edges tool in Rocket3f to solve your problem. I seriously doubt subdivide will help....probably make things worse.

It happens mostly with holes because of the thin slivers created when the model is triangulated.

Either way your going to have to retopo these models to get good results.

[ambiroa]

Tried it with the hard edge tool, didn't work.

Thank anyway Phil, for all the help.

[PhilProcarioJr]

@ambiroa

Can you share your .obj file?

[ambiroa]

Yes I can. Let's see if attaching my file goes well.

[PhilProcarioJr · Accepted solution]

@ambiroa

Ok this is very easy to fix with Rocket3f.....

Open your .obj file

select the model

As I said before using the hard edge tool....just hit the O key on your keyboard (not zero) this sets all your hard edges.

Now save out your fixed .obj file

[PhilProcarioJr]

@ambiroa

[ambiroa]

OMG Phil, that's the solution!! Thank you so much!

The reason the first time it failed, I specifically selected the area of the errors, and then hit O. this time I did what you said, selecting the entire mesh and hit O. Just checked it in substance and it looks great now. Only thing I need to fix is two horizontal lines on the valve's main body, I guess you've seen them as well.

But again thank you for taking the time to help me out and even downloading and installing Rocket for it.

So happy to know I can keep working in Fusion 😄

[PhilProcarioJr]

@ambiroa

Your welcome.

"Only thing I need to fix is two horizontal lines on the valve's main body, I guess you've seen them as well."

Yes I saw that but I figured you could take care of that part. 

Post your final results in Unreal engine 4 when your done I would like to see them.

Cheers

Phil

[ambiroa]

Will do, once I learn how to properly use UE 😉

I will post an image rendered in Substance Painter's Iray. I just need to give it grit, weared edges, rust, and the key element, blood spatters 😄