topic Re: Complex STL Mesh in Fusion Design, Validate & Document Forum

Complex STL Mesh

tom.frankee1991 — Wed, 15 Jan 2025 11:55:39 GMT

Hey there

i have issues to convert a very complex stl/obj mesh from blender into a solid body or any other type which i can use as parting tool.

I want to create a negative mold for a silicone cast. Therefore, it's enough for me to use the mesh as a parting tool. However, this doesn't work. I dont understand why it is listed under solid bodys, but i cant select it as tool. Ive already tried a tutorial with instantmesh and then converting it in T Splines in the freeform environment in fusion, but this destroys important details.

Re: Complex STL Mesh

TrippyLighting — Wed, 15 Jan 2025 12:16:48 GMT

In order to transfer that fine detail, you need to use a higher polygon count. The area where the text is embedded in the pillow is particularly challenging and might need some corrections after re-meshing.

While I am typing this Blender's quadriflow remesher is working on the mesh. I se the polygon count to 40k.

We'll see what that does. If that doesn't provide acceptable results I'll try my favorite tool, InstantMeshes. Can you provide a link to the tutorial you followed?

Re: Complex STL Mesh

TrippyLighting — Wed, 15 Jan 2025 12:25:53 GMT

Is this really the scale you were looking for?

Re: Complex STL Mesh

TrippyLighting — Wed, 15 Jan 2025 12:48:57 GMT

Also, the embedded text/'letters and the ridges are separate mesh object. While that remeshes (in Blender) it will create obvious problems when trying to mold/demold a part, even when using a soft silicon mold.

I would probably join (boolean?) those to the main mesh before remeshing and smooth the transitions with sculpting tools in Blender, or Autodesk Meshmixer.

I separated those objects into a different mesh in Blender and then had to correct one area manually (delete and re-fill faces) where the re-mesher created overlapping polygons.

Then it converts fine into a T-Spline in Fusion.

Re: Complex STL Mesh

tom.frankee1991 — Wed, 15 Jan 2025 12:49:38 GMT

Hey

i was follwing this tutorial

https://www.youtube.com/watch?v=aMZKgzBpodI

And sorry, thats not the correct scale. Its just 400mm wide

Instead Instantmesh, ive used Quadmesh in Rhino which was faster.

Now i stuck at the part where i converted quadmesh faces into t splines, it doesnt let me close the freeform mode

Re: Complex STL Mesh

tom.frankee1991 — Wed, 15 Jan 2025 13:00:21 GMT

Thanks a lot for your effort!
The problem is, i didnt model this body in blender, its from the client. I just need to get a negative version of it to 3D print the cast.
Since there is no direct contact to the client, i cannot ask for another model. Honestly said, this mesh/freeform environment is pretty new to me.
Is it possible to create a negative form in blender? And would you like to share the model from blender?

Re: Complex STL Mesh

tom.frankee1991 — Wed, 15 Jan 2025 13:15:04 GMT

Finally it worked!

Why the hell is that so complicated?
Fusion was crushing several times to convert quadmesh to breps

Re: Complex STL Mesh

TrippyLighting — Wed, 15 Jan 2025 13:40:39 GMT

@tom.frankee1991 wrote:

Why the hell is that so complicated?

Because remeshing and T-Spline and NURBS math and algorithms aren't trivial by any means.

Re: Complex STL Mesh

laughingcreek — Wed, 15 Jan 2025 15:45:02 GMT

@tom.frankee1991 wrote:...
Is it possible to create a negative form in blender? ...

Yes, and if you're going to work with this type of mesh object with any regularity it would be well worth it to learn how. fusion isn't a very good tool for this type of thing.

Re: Complex STL Mesh

TrippyLighting — Wed, 15 Jan 2025 17:12:28 GMT

@tom.frankee1991 wrote:

https://www.youtube.com/watch?v=aMZKgzBpodI

I created that tutorial 😉

Re: Complex STL Mesh

TrippyLighting — Wed, 15 Jan 2025 17:14:08 GMT

I would also do this in Blender, but regardless which too is being used, the letters still aren't properly attached to the main pillow.

This will require some modeling work before it can be turned into a mold.

Betreff: Complex STL Mesh

tom.frankee1991 — Thu, 16 Jan 2025 07:16:04 GMT

Hey Guys

thanks for your help
Just a general question:

There is no actual tool to cut a solid body with a mesh like in rhino (meshbooleansplit)?
And is it normal that it takes a while to transform quadmashes into breps in fusion or is it just my computer?

Which is still confusing to me. If i cam creating a face which has the same orange mesh symbol, i can cut any solid body.
but with the imported mesh i cant!

Betreff: Complex STL Mesh

TrippyLighting — Thu, 16 Jan 2025 12:40:36 GMT

@tom.frankee1991 wrote:

...
There is no actual tool to cut a solid body with a mesh like in rhino (meshbooleansplit)?
And is it normal that it takes a while to transform quadmashes into breps in fusion or is it just my computer?

Nope!

Yes! Again, this isn't trivial!

@tom.frankee1991 wrote:

...

Which is still confusing to me. If i cam creating a face which has the same orange mesh symbol, i can cut any solid body.
but with the imported mesh i cant!

The orange symbol you see in the browser when creating a face is likely the symbol of a surface body, not a mesh body.

If you can create a screenshot or even better a screencast we can confirm (or not).

Re: Complex STL Mesh

adam.helps — Fri, 17 Jan 2025 16:48:56 GMT

TrippyLighting is right. Those algorithms are very complicated. The problem is that meshes are made out of a large number of flat pieces. They approximate curvature with thousands and thousands of perfectly flat planes. If you could run your finger over the surface of all but the densest meshes, you'd feel thousands of sharp edges, similar to the surface of a crystal. That representation makes for poor quality CAD models, where having thousands of sharp edges would cause excessive face counts and a high failure rate with solid modeling tools.

The algorithms are guessing the intended curvature by looking at the relationships between all of the faces on the mesh. It then fits thousands of curved surfaces to groups of faces in order to reduce the overall face count (usually by a factor of hundreds to thousands). Finding the boundaries for the curved faces and fitting curved functions to them is a heavy lift for your computer.

It would be much simpler to just directly convert the shape with no changes, but the CAD model that results would be so heavy that it would be completely unusable.

Re: Complex STL Mesh

hfcandrew — Fri, 17 Jan 2025 20:57:44 GMT

Token hfcandrew response: If you have a mesh, use Meshmixer.

You can do all this in Meshmixer with no loss to detail.