OBJ Mesh To Solid Issues

[aaronsYVQQR]

I have this OBJ model that I am looking to modify. When attempting to convert it from mesh to solid, 1- it does take awhile based on the 10000+ facets it has to compute, and 2- when it does complete parts are missing, its basically a unstitched surface and/or I have an added sphere from out of no where. I have repaired, rebuilt and stitched this obj file several times resulting in either incomplete solid/surface or a surface with unexpected added features. I tried to convert as a base feature, facets, parasmatic, change the amount of mesh faces to lower the accurate details. Everything has resulted in a screwed up looking model. I will attach a photo of what I see and the obj file unmodified for someone else to attempt.

[michael.woodrum]

The OBJ is missing. However, I will say that I rarely have a good result in fusion attempting to create a solid from something even slightly complex.

I know that is not what you want to hear as an answer. That is something I have been frustrated with several times in the past. Most of the time, I end up modeling the object from scratch. If I have access to the actual measurements. It is faster than attempting to repair in fusion through any workflow provided yet.

Another thing I have been able to get away with, depending on what I plan on doing to create the object in real world, is using the model surface to machine on my cnc. I do not try to take something with any detail and convert. If it is on something, line a panel for example, I can import my object and place it within the model and when I machine I can machine the surface of the imported object without issue. I cannot modify anything though.

It would be amazing to be able to import complex objects, draw 3d sketches and project points from the imported object. Then create dimensions and angles to represent the objects surface directions. Something to be able to give fusion a guide on how to reproject the original object to a converted mesh. as of now, the best I have ever actually done is get a faceted object that I still spend too much time repairing.

Meanwhile, and I know this is not the same thing as fusion, I can open the freely available on my computer "3D Builder" drop in objects and subtract, add, scale and repair with little effort. it is my go to for certain things. Nothing engineering grade for sure. Quick changes to something are actually possible though. i would assume with the myriad of experience autodesk has with 3d in every area, this could be solved. Not yet though. It must be harder to solve than it seems. At least when you are creating a software package that is built from the ground up.

I also use Zbrush and I can have millions of polygons without issue. boolean operations easily combine thigns. Different beast, I know. I jsut have to find hacks to get around the limitations of fusion. I hav ebeen using it since the early days too. Jumping from inventor to fusion after the capabilities were basically on par with each other. 

If someone else jumps in and gives an answer by showing them actually turning it into a working model, i would love that. My guess is that it will not happen.

[aaronsYVQQR]

Would the microsoft 3D app help modify your model in order to make a working model to use as a solid part?

[michael.woodrum]

It's possible you could split the part into multiple parts. Convert and
then combine in fusion. Maybe.

[TheCADWhisperer]

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@aaronsYVQQR wrote:

I have this OBJ model …I will attach a photo…

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Zip and Attach the original *.obj file here.

[aaronsYVQQR]

I cannot even upload the file via .obj or .f3d  must be that bad of a file

[TheCADWhisperer]

My previous instruction was to ZIP the *.obj file before attempting to Attach here.

Are you on Windows or are you on Mac OS?

[TrippyLighting]

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@michael.woodrum wrote:

... Jumping from inventor to fusion after the capabilities were basically on par with each other... 

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Let's agree that this applies to the subset of features you might have used in Inventor.

[michael.woodrum]

Agreed. Basically was in the sentence.

I miss a bunch from inventor for sure. However, the cam and plugins I use
with fusion to do layouts for jobs is amazing. I had to purchase the
add-ons to get what I need. Well worth it.

The parametric design features of fusion are also great.

I had to come up with work arounds or learn a completely different method
in fusion but, I can do most things

[TrippyLighting]

To upload a .obj you have to zip it first.

The model you are trying to convert was not designed with CAD or solid modeling in mind. It was modeled in a Sub-D modeling package, for example 3DS Max, MoDo, Cinema 4D, Blender etc. for visualization, not for manufacturing.

That has certain implications. Quad-meshes created in a Sub-D modeler are much more forgiving and you don't have to worry about possible self intersections. That is particularly the case for visualization-only models. If it can't be seen then it's OK. When modeling for visualization, it is also a complete waste of time to create a watertight model, again, if that cannot be seen.

However, when you want to manufacture something, this changes. For 3D printing, for example, a mesh has to enclose a volume watertight. Then you can create a .stl directly from a quad mesh and if modeled properly, the quality of that .stl mesh is much higher then what you get out of a CAD package.

Now lets enter CAD into the equation. Fusion 360 is one of the few CAD packages that allows users to covert a quad-mesh into a T-Spline and then NURBS surface or BRep (solid body). A T-Spline is really only an intermediary representation of geometry and the goal of it is to convert the T-Spline then into a (NURBS) surface body or solid body. There are technical requirements that have to be met in order for that to work.

CAD generally works with NURBS surfaces and requires that the polygon mesh does not create self intersections.

When trying to convert the "engine" mesh from a T-Spline to a surface (it's an open mesh so won't convert into a solid body) I get these errors that are also highlighted by Fusion 360 in the viewport:

You can try and attempt to fix those in Fusion 360, but I personally would take the .obj into Blender and fix these things there. It might take a few attempts until it converts into a Surface body.

[TrippyLighting]

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@michael.woodrum wrote:
Agreed. Basically was in the sentence.

I miss a bunch from inventor for sure. However, the cam and plugins I use
with fusion to do layouts for jobs is amazing. I had to purchase the
add-ons to get what I need. Well worth it.

The parametric design features of fusion are also great.

I had to come up with work arounds or learn a completely different method
in fusion but, I can do most things

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Yep, the Cam stuff is really very good!
So are the parametric features.

[michael.woodrum]

If you've never used blender before, your going to be on a learning path
for a while to get comfortable enough with the interface alone. Then
concepts that would allow you to fix this might take longer. At the least,
you've got a solid week of learning to get to a point in which you will be
able to really figure it out.

Blender is amazing and I've used it for years. I'm still figuring things
out sometimes though.

This is why I suggested using 3d builder in windows. If it's not already on
your star menu, it's in the store. Open the model and it will let you know
on import that it's not water tight.
If you've used resin printers, this tool is great for repairing non
manifold models.

When it yells at you about it, click repair and wait. You may get something
you can use from it. If the complexity is too high for fusion though, it
may not allow you to process it.
You could attempt to reduce polygon counts in blender by decimation or
retopilogy tools. That's where it gets complicated though.

You can also try to break the model into sections to convert in fusion. In
3d builder, use an object to cut the object and create pieces of the object
that can merge back after converting in fusion.

[TheCADWhisperer]

@michael.woodrum 

Did you try your suggestions with the OP’s geometry?

[michael.woodrum]

No. I know the f3d file is there. If the original obj is attached, I'll try with that. Exporting it back out of fusion to obj and then doing the corrections outside and importing back in, has to have conversion occurring right?

I've said from the start though, if you cannot simplify it before importing you'll have issues. It's hard to import complicated meshes. Make them simple before if possible. Of just trying to learn how to work around this, spend all the time you want trying to get it working.

If you're trying to actually get something done and it takes less time to remodel from scratch in fusion, that's the way to go.

You'll have better chances of getting it to work using 3rd party utilities to repair and simplify what you're planning to import. 

[TrippyLighting]

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@michael.woodrum wrote:

've said from the start though, if you cannot simplify it before importing you'll have issues. It's hard to import complicated meshes.

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Can you specify "complicated"?

Just to be clear, T-Splines are mathematically a lot more complicated than quad meshes. But I've not had problems importing T-Sline meshes with 40,000 and more polygons. As long as the quad mesh is properly modeled and does not create self-intersections that usually work perfectly fine.

[michael.woodrum]

First, make sure it's water tight at the least.
I've tried bringing in many meshes that are perfectly fine in blender or
zbrush. 40k polygons is not a lot when bringing in detailed objects. So, I
usually just use the mesh in CAM since that's what I use mostly.

However, bringing in downloaded models to attempt modifications can be
tedious if attempting to convert. If I can simplify outside of fusion
faster than fusion can convert, then I'll do that. I then try to project
points from the converted mesh to make a more accurate model for real world
use.

If you can get this model from the op to function well, great. Sometimes,
it can be worth the time. Sometimes it's easier to model from scratch
again. Depends on how much energy you are willing to spend.

I'm sure that the converted model shown in a reply that has issues still,
even after fixed, will be faceted and nowhere near what you want in
reality. It would be better to just use modeling tools to approximate the
original. Use the original as the template.

[TrippyLighting]

@michael.woodrum thanks for the tips. I've used CAD software professionally for over 30 years and more than 20 of those in 3D. I've used Blender for 18 years.

[TheCADWhisperer]

@aaronsYVQQR 

Where did you go?