Confused about Mesh to Brep in Fusion360

[ricotte]

I have a program that generates surfboard fins in stl files with lots of triangles, and I'm trying to import these files into Fusion360 to use the Cam functions.  In practicing, I created an stl file with 9798 triangles that I tried to change to BRep (so I can use the CAM functions).  I've reduced it to several different numbers of triangles using Meshmixer, but the problem I'm having is that  I cannot figure out why sometimes mesh to BRep works, and why other times it gives an error message.  It seems to be dependent on something other than the number of triangles.  So, for example, if I use Meshmixer to reduce a flat side 95%and the curved side 70%, I end up with 1656 triangles, but get an error message in Fusion360 when I try mesh to BRep.  However if I use Meshmixer to reduce the whole object 76% to 2354 triangles, mesh to BRep works fine (75% reduction with 2484 triangles will not work).  I do not know why I it works with 2354 triangles but I get an error message with 1656 triangles.  

I'm a beginner with Fusion360, and any insight into the best way to convert files with lots of stl triangles to BRep would be appreciated.  If there is a better way than first using Meshmixer, I'd be glad to hear about it.

(in case you're interested, I've uploaded the two files I discussed to my dropbox account at:

https://www.dropbox.com/s/21ljb7tztxfpe02/testfin1.mm76.stl?dl=0  (the 2354 triangle one that works)

https://www.dropbox.com/s/ftz6sxel10sh21m/testfin1.mm95flat.70curved.stl?dl=0  (the 1656 triangle one that doesn't work)

Thanks,

Ric

[tkuechle]

So that you know, Meshcam CAM software only accepts polygon formats, STL (and possibly DXF?). Several other CAM apps also only accept polygon file types. 

if you were to buy MeshCam, its very affordable, you could begin creating gcode from your file as is. I'm still learning to use my CNC machine, a Nomad 883 from Carbide3D, it comes with MeshCam. Good Luck. 

PS- I've been surfing since 1983, and have fixed many dings over the years. I have only snapped a fin in 2 twice and tore off several on reef and shore poundabout 10 times.

[colin.smith]

Hi Ric, 

I'm not sure why you are seeing the inconsistency in the Mesh > BREP converter. Generally, this is not an ideal solution because the number of faces in the mesh must be relatively small (10,000) faces in order to convert and utilize in subsequent operations.  We put the funcitonaly in as a stop gap measure, but it uses desktop computing to do the conversion so meshes higher than 10K faces can take a long time to convert.  In the future I would like to see this being converted in the cloud, but that isn't available today.

I'll grab your files and see what our dev team can come up with.

Colin

[ricotte]

Colin, I appreciate any insight you can give me as to why I'm having problems.  The original file (before reduced with Meshmixer) was almost 10,000 triangles.  When I try to convert it with about 2400 triangles (77% reduction), it happens almost instantly on my desktop.  With the files that I get the error on, I'm not seeing a long wait; I get the error message instantly.  That makes me think I'm simply doing something wrong, and that it wouldn't matter if it could be converted in the cloud.  In case it matters, I'm using a Mac laptop with build 2.0.1484.  

tkuechle, I wish I'd been surfing for 20 years.  I've never broken a fin, but a friend of mine is a shaper, and he's got me interested in making some custom fins.  I am aware of Meshcam, and at some point may need something like that, but was hoping I could get this to work in Fusion360

Thanks--I appreciate your helping me with the learning curve,

Ric

[San_Escobar]

Hey folks.

I am always striving to find a software that facilitate my life regarding to reverse engineering. 
When I first saw it on Fusion 360 showreel (PULL Tool), I couldn't believe that it was that simple. EYE MELTING!!!

As matter of facts, I have carried out some test on it and self experience I can say, it is not as simple as it looks, and what I can say is that it only work if you have a high-poly mesh, which will possibly be high resolution model. As I got a very rough mesh produced out 123D Catch and F360 (VERY VERY Low resolution) and F360 didn't like it at all. pretty much the resolution as on your have on your (the 2354 triangle one that works) by all means rough. I have even, split the mesh in few bit in Alias to see if it facilitate but still not success still. 

Summarising, no matter the tessalation, if you have a High Resolution mesh it works, but if its low, than SORRY!

I will try your models later and see what happen. I will be back!

Cheers.

[gautham_kattethota]

Hi Ric,

The problem you are seeing is not due to the number of triangles at all.  Fusion360 imposes a restriction of 10K triangles while converting from mesh to brep, due to performance reasons.  Anything under that is fine. Fewer triangles does not necessarily mean the chances of success improves during the conversion.  I looked at your file with fewer triangles and there appears to be some badness in the stl file which results in our geometry kernel returning an error during conversion.  I will work with that team to understand what the issue exactly is and get back to you.

I opened this file in MeshMixer and remeshed the flat part of the mesh, creating smaller triangles in this region.  This resulted in a successful conversion to brep after importing that stl file into Fusion.  I dont think you needed to reduce the number of triangles on the flat surface to that extent.  In the future, if you encounter an stl file with more than 10K triangles, try to reduce it just enough that FUsion360 can handle it (under 10K).  This will help retain the geometries as close to the original design as possible.

Hope this helps.
Gautham

[gautham_kattethota]

Hi Ric,

One more thing - the mesh appears to be too small when imported into Fusion360.  Without applying any scaling, the heigth of the part is under 1mm!  You mentioned that you saved the stl file from Meshmixer. In the software where you are designing this, what is your default units?  If you want to specify units while importing an STL file into Fusion360, you can use the "Insert Mesh" command under the INSERT dropdown in the command panel.  This allows you to specify incoming units for the stl file.  But note that this command is only available in a "Direct Modeling" document, not in the parametric document.

Gautham

[ricotte]

Hi Gautham,

Thanks very much for this info.  The original stl files are just under 10,000 triangles, and I get error messages when I try to convert them to BRep.  I simply assumed the problem was the number of triangles (for no good reason evidently).  If you'd like to look at the original file (before I reduced it with Meshmixer), you can find it (and another file I have trouble with) at:

https://www.dropbox.com/s/v3xd5g5p521p9zi/testfin1.stl?dl=0

https://www.dropbox.com/s/z94kbuyr2z6o7sj/johnnyricefin.stl?dl=0

I get an error message immediately when trying mesh either of these to BRep, even though both of the files contain almost 10,000 triangles.

(I tried to remesh the 2nd file, but the result didn't look very much like the original; I need more practice with that)

Thanks very much,

Ric

[ricotte]

Yes, I knew the mesh showed up small when imported, and I usually scaled it soon after import.  I haven't been using the import mesh function, but when I use it and set the units to meters, it is imported at about the right size.  I was using inches as the default on the original program, but it is clearly not outputting in inches.  I didn't think that the small size was a problem, as long as I scaled it up on import, but I could easily be very wrong.

Thanks,

Ric

[gautham_kattethota]

Hi RIc,

The originals models look great!  Its a bummer that you  ended up with big distortions trying to reduce the number of facets on those models.  Anyway, all these models result in the same error internally.  The number of facets was not a problem.  Both report under 10K.  I will work with the geometry team to identify the cause of this and try to address this soon.  

And, yes, the scale of the model is not contributing to this error.

Will get back to you sometime soon with an update.

Gautham

[ricotte]

I downloaded an update a few days ago, but the problem still persists.  By trial and error I have found that if I first remove duplicate vertices in Meshlab, then I still cannot use Mesh to BRep, but I can click Convert, which will change it to T-Splines.  If I then try to Convert T-Splines, I get an error message that says "Edges or Faces may be crossing."  I still haven't been able to get a version that I can use the Cam function with.

I'm beginning to wonder if the problem may be that my laptop simply doesn't have enough computing power to work with files like this.  I sometimes get the message that my graphics memory is low, but there isn't much I can do to increase it on this machine.  

Thanks

Ric

[gautham_kattethota · Accepted solution]

Hi Ric,

The conversion issues with these stl files have been fixed, but it will come out in the July release of Fusion360.

Deeper investigation into these datasets revealed a problem with some facets, wherein one or more facets had a zero length edge.  This was leading to the failure during the conversion.  Our geometry team has fixed the issues related to this.  Such facets are now healed so that the conversion results in a good solid brep body.

Just curious, which software were you using to write out the STL files?

Thanks for reporting this issue.

Gautham

[ricotte]

Hi,

Thank you very much for the update.  I really appreciate all the work that has been done to illuminate and fix this issue.

I generated the files in a two-step process.  First I used FinFoil to get the design, and then Finfoil stl export to get the stl files.  you can see them here:

http://hrobeers.github.io/finFoil/

http://hrobeers.github.io/finfoil-web/              (this creates the stl files from FinFoil's foil files)

Thanks again,

Ric

[Anonymous]

Hi Colin,

You mention here that the small 10,000 polygon limit for the brep conversion is just a stop gap measure. Any ideas when this might be improved in the future? Have there been any developments since this post? I'm hoping to cnc quite complex detailed models for sculpture, and this really low 10,000 polygon limit has me rather disappointed. 

Any news would be appreciated, Thanks.

Haywood

[colin.smith]

Hi @Anonymous,

We are looking at ways to better handle mesh data.  Can't promise anything yet but there should be some improvement in the coming year.

Thanks

Colin

[tkuechle]

I wonder if also converting the triangles to quads would help in the conversion process? This might be a good option . I have been toying around with this workflow with some success using other apps. Of course those features will probably be integrated into Fusion360 eventually. 🙂

[colin.smith]

@tkuechle - that is essentially what we are looking at doing.

The problem with the 10K limit isn't that we don't have the ability to do it. The problem is that with the triangle mesh to BREP conversion it would take each triangle of the mesh and make it a BREP face.  So essentially you end up with a BREP with 10K faces.  This would probably drag Fusion to the ground.

So what we have been looking at is converting the triangle mesh to a quad mesh.  That quad mesh can then be converted to a T-Spline.

The T-SPline to BREP converter is pretty efficient with the creation of faces so we expect this would result in a BREP with much fewer than 10K faces and it would be smooth due to the quad to T-Spline conversion. 

So we want to do Triangle Mesh > Quad Mesh > T-Spline > BREP

The trick is not to alter the shape of the object as is moves through these different translators. 

Hope that is clearer.

Colin

[tkuechle]

Hi Colin,
Yes, that's a more complete explanation of what I typed, thanks.
Tem

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