Insert Mesh for OBJ files seems to skip the "surf" statements in the OBJ file

[Anonymous]

When I insert an OBJ file into my otherwise empty mesh, Fusion 360 displays all the "f" (face) objects in the OBJ file accurately, but none of the "surf" (surface) objects in the same OBJ file.

It is entirely possible that there is something with the surf statements in my OBJ file -- I generate them using a Java program, and I am new to CAD.  So, I put away my Java program, and imported example OBJ files from http://www.cs.utah.edu/~boulos/cs3505/obj_spec.pdf. Same problem! Again, "f" objects show up, and "surf" objects do not.

What gives? Is there a bug in the way Fusion 360 imports the "surf" objects in OBJ files?

Three examples follow, all from http://www.cs.utah.edu/~boulos/cs3505/obj_spec.pdf. First one has only "f" objects, and Fusion 360 handles it just fine. The second and the third contain only "surf" objects, and Fusion 360 shows nothing for either.

Thanks for your patience and help.

Example B1-21: Fusion 360 handles this one just fine.

v 0.000000 2.000000 2.000000

v 0.000000 0.000000 2.000000

v 2.000000 0.000000 2.000000

v 2.000000 2.000000 2.000000

f -4 -3 -2 -1

v 2.000000 2.000000 0.000000

v 2.000000 0.000000 0.000000

v 0.000000 0.000000 0.000000

v 0.000000 2.000000 0.000000

f -4 -3 -2 -1

v 2.000000 2.000000 2.000000

v 2.000000 0.000000 2.000000

v 2.000000 0.000000 0.000000

v 2.000000 2.000000 0.000000

f -4 -3 -2 -1

v 0.000000 2.000000 0.000000

v 0.000000 2.000000 2.000000

v 2.000000 2.000000 2.000000

v 2.000000 2.000000 0.000000

f -4 -3 -2 -1

v 0.000000 2.000000 0.000000

v 0.000000 0.000000 0.000000

v 0.000000 0.000000 2.000000

v 0.000000 2.000000 2.000000

f -4 -3 -2 -1

v 0.000000 0.000000 2.000000

v 0.000000 0.000000 0.000000

v 2.000000 0.000000 0.000000

v 2.000000 0.000000 2.000000

f -4 -3 -2 -1

Example B1-29: Fusion 360 fails to show any "surf".

g bspatch

v -5.000000 -5.000000 -7.808327

v -5.000000 -1.666667 -7.808327

v -5.000000 1.666667 -7.808327

v -5.000000 5.000000 -7.808327

v -1.666667 -5.000000 -7.808327

v -1.666667 -1.666667 11.977780

v -1.666667 1.666667 11.977780

v -1.666667 5.000000 -7.808327

v 1.666667 -5.000000 -7.808327

v 1.666667 -1.666667 11.977780

v 1.666667 1.666667 11.977780

v 1.666667 5.000000 -7.808327

v 5.000000 -5.000000 -7.808327

v 5.000000 -1.666667 -7.808327

v 5.000000 1.666667 -7.808327

v 5.000000 5.000000 -7.808327

g bspatch

cstype bspline

stech curv 0.5 10.000000

deg 3 3

surf 0.000000 1.000000 0.000000 1.000000 13 14 \

15 16 9 10 11 12 5 6 7 8 1 2 3 4

parm u -3.000000 -2.000000 -1.000000 0.000000 \

1.000000 2.000000 3.000000 4.000000

parm v -3.000000 -2.000000 -1.000000 0.000000 \

1.000000 2.000000 3.000000 4.000000

end

Example B1-30: Again, Fusion 360 fails to show any "surf".

v -5.000000 -5.000000 0.000000

v -5.000000 -1.666667 0.000000

v -5.000000 1.666667 0.000000

v -5.000000 5.000000 0.000000

v -1.666667 -5.000000 0.000000

v -1.666667 -1.666667 0.000000

v -1.666667 1.666667 0.000000

v -1.666667 5.000000 0.000000

v 1.666667 -5.000000 0.000000

v 1.666667 -1.666667 0.000000

v 1.666667 1.666667 0.000000

v 1.666667 5.000000 0.000000

v 5.000000 -5.000000 0.000000

v 5.000000 -1.666667 0.000000

v 5.000000 1.666667 0.000000

v 5.000000 5.000000 0.000000

# 16 vertices

cstype cardinal

stech cparma 1.000000 1.000000

deg 3 3

surf 0.000000 1.000000 0.000000 1.000000 13 14 \

15 16 9 10 11 12 5 6 7 8 1 2 3 4

parm u 0.000000 1.000000

parm v 0.000000 1.000000

end

# 1 element

[jeff_strater]

Thanks for the post, @Anonymous.  Unfortunately, today, Fusion treats OBJ as just a mesh format.  That is, we import only mesh data from OBJ, which is exactly what you have observed.  If this is a common workflow, please create a new idea on the fusion 360 ideastation, and see if others agree.

Jeff Strater (Fusion development)

[Anonymous]

Jeff,

Thank you for the quick response. I can see why it makes sense for  "import mesh" to skip surfaces. I may still request an enhancement at fusion 360 ideastation.

While I have the attention from you and this forum, let me ask if there may be a workaround for my immediate task. Here is my immediate task: Help my son (will be a 9th grader this fall) design an impeller before he gets to buy his own 3D printer. The Java code prints an OBJ file, and the mesh points show up in Fusion 360 just fine after insert mesh. We now need some way to specify the surfaces that connect those mesh points. This cannot involve point-and-click in Fusion 360. There are over 5k mesh points, and we must to be able to change the whole design by editing parameters in Java code.

I can understand why insert mesh skips surfaces. But, ....

Q1) Is there any other way an OBJ file can specify which sets of mesh points comprise the sets of vertices of surfaces? (Geez! That sounded bad. I guess I am asking if there is a way to specify a surface without calling it a "surf". 🙂

Q2) If not Java+OBJ, is there another language+specs combination that we can use to generate mesh+surfaces?

Thank you.

[jeff_strater]

Hi, sorry for the slow response.  I had somehow lost the notification that you had responded.

Anyway, I think I have a picture of what you are trying to do.  You have an OBJ file that is generated programmatically that you want to insert into Fusion, but you want the output to be surfaces.

There are a couple of approaches.  You can directly convert a mesh to a surface, using the Convert command while in Sculpt mode.  Here is the basic workflow:

the command is in the Modify pulldown:

select the mesh

The result is a new Surface Body:

However, this is only really effective if the number of facets in the mesh are relatively low.  If there are a lot of facets, performance will be bad after the conversion.

Another, more labor-intensive method is to use "object snap" in TSplines.  Some commands (primarily Create Face and Edit Form) have an Object Snap mode.  This will allow you to essentially "reverse engineer" surfaces from the mesh.  This allows you to end up with surfaces that are less dense than the input mesh, but it does take some time and patience:

Hope that one of these will work for you.

Jeff

[TrippyLighting]

I would add to Jeff's post that the number of polygons in your mesh really is unnecessarily high. I'd try to lower it and see if you can create a good T-Spline from a lower resolution mesh and then hand edit the T-Spline where necessary.