topic Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect in Fusion Design, Validate & Document Forum

How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

aaron.markstaller — Thu, 17 Feb 2022 10:37:10 GMT

I've modeled a surface with t-spline bodies that is supposed to be like an envelope open for a plant pot. Then I've tried to add thickness to it to create walls so it can actually be a solid body instead of a surface body, but can't get anything to work since it always intersects another part of the body. Then it delivers the error that it cannot finish the form since it is intersecting itself. I would usually add thickness in the t-spline form and clean up the box view, or finish the form then add thickness with the surface to solid body thickness tool; and last case duplicate the surface and shrink it then create a loft between the two, but these don't work because they all intersect.

Is there some way to get around this error so that it can intersect itself, and just create the solid body like it is showing in the T-spline view? I don't want to go and make each surface barely not touch each other surface and then go near zero thickness at the corners because I want them to be strong and I want it to be watertight.

What workarounds are there for getting a body to just let it self-intersect? Just combine the intersections.

I find I need this quite often working with surface bodies and t-splines.

Thanks

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

TrippyLighting — Thu, 17 Feb 2022 12:07:16 GMT

Export the control cage as a .obj before thickening.

Import into Blender.

Apply Solidify modifier.

Export .stl from Blender.

3D print.

Done!

Or you can tray to follow a convoluted workaround someone else might post.

Sometimes you just need to use another tool.

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

aaron.markstaller — Wed, 23 Feb 2022 04:59:58 GMT

Nice. If Blender's solidify works well often, then looks like I'll be using it a lot lol. Thanks

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

aaron.markstaller — Wed, 23 Feb 2022 05:02:02 GMT

It shows the thicken command fine, but just does not allow the solid to be created if it intersects itself,

So maybe have to split the surface, then thicken into separate bodies, then combine the bodies.

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

hamid.sh. — Wed, 23 Feb 2022 05:54:11 GMT

If you Do not Capture Design History you can use Boundary Fill to convert your self-intersecting form to BRep. Afterwards you can enable history back.

However, you'll get these kind of things which no CAD software likes and I am not sure if that makes problem in 3D printing:

There may be ways to eliminate this, e.g. 0 surface offset from BRep and Trim, but I didn't yet.

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

hamid.sh. — Wed, 23 Feb 2022 08:30:29 GMT

@aaron.markstaller OK, I posted the above workaround but I regret it, especially after trying to eliminate those intersections. It's really just a "convoluted workaround" as @TrippyLighting put it. I would say follow his advice and do it in Blender. Fusion is not made for this.

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

aaron.markstaller — Wed, 23 Feb 2022 11:40:35 GMT

When I solidify, how do I round or bevel the edges? Or keep the curvature of the model instead of having it tessellate into faceted control points? I see the bevel options but the solidify faceted it, so now I can't select one large face, it has each face between points.

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

TrippyLighting — Wed, 23 Feb 2022 12:19:31 GMT

"Facepalm" I had not even remotely thought of the boundary fill tool! Great technique!

Correct, most CAD software hates these kind of self-intersections, but for most slicer software for 3D printing these self intersections do not pose a problem. At least this way the object can be completed in Fusion 360.

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

TrippyLighting — Wed, 23 Feb 2022 18:51:50 GMT

1. I solidified to the outside, not the inside.

2. I applied a bevel modifier

2. I applied a Subdivision modifier

Zipped Blender file is attached.

Re: How do I work around self-intersecting geometry error for t-spline body when I need geometry to self-intersect

hamid.sh. — Thu, 24 Feb 2022 02:26:02 GMT

Yeah Boundary Fill works (only when design history is off, so form body is accessible for every tab) and now I understood that it is also usable for 3D print, but not for anything beyond that. Even fillet doesn't work on it. Just as you said it, this task needs a different tool.