When sculpting insert edge modifies the geometry drastically

[Anonymous]

I've created the majority of my geometry and now I want to add a new edge to give me a little more control.  Adding the new edge moves ALL of the existing geometry.  I basically have to edit every single vertex again.  Here's the before, the preview, and the after is nothing at all like the preview.  How do I insert and edge and keep the rest of my geometry from moving all over?!?

I am finding lofting airplanes in Fusion 360 to be an almost impossible task. This is the 8th CAD/3D Design program I have learned to use and I am struggling after a year as a hobbyist.  Any links on how to create an accurate scale model of real airplanes would be great!

[Beyondforce]

Hi @Anonymous ,

I'm not sure the Sculp environment is the right approach in your case. I have just created a series of videos on how to design an airplane in F360, please check it out:

https://www.youtube.com/watch?v=Va39Zlrm4EU&list=PLjGKAi--ZCoZntY2C0JwUjp-FZvqQUgOl&index=4

If you have any question, please let me know.

Cheers / Ben

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[jeff_strater]

there is also the "exact" mode for Insert Edge.  If this option is chosen, the existing geometry will be preserved, but the resulting model will be more complex (can insert more than one edge):

[laughingcreek]

it's also important to wrap your brain around the fact that it's the TOPOLOGY of the t-spline that determines it's shape.  change the topology (ie add an edge) and you are going to change the shape. (unless you use exact mode, which will likely add a bunch of edges that can make future edits more difficult.)

if you where to look at the model in box mode, you would see that the control points that are used to interpret the shape of the tspline didn't move.  

[davebYYPCU]

I disagree with Ben, and think that Sculpt might do a better job than the modelling area.

Comes down to how accurate you wish to be, and how good is the documentation you can source. 

My canvass is not the same as yours.  Under the wing is a separate piece in my documentation.

BD5 is quite a challenge to get right.

Would like to get up to speed in Sculpt, but that takes time to understand the fluid results of small changes, seems I am about your standard on Sculpt.

Not happy with my modelling result so far, too much oil canning, and considered going to sculpt after this....

Might help....

[davebYYPCU]

I checked out #7, about half of it, not enough accuracy demonstrated to the fidelity of the canvasses, for me.

[Anonymous]

Great video series.  I watched #7 and picked up some great tips!  The BD-5 is a little more complicated in that the fillet is non-linear on the rear half of the fuselage so I'll have to loft or sculpt it.

I will watch the entire series, this is awesome!

[Anonymous]

I tried that but didn't get the results I expected.  I'll have to experiment more. Thanks!

[Anonymous]

That's the rub. I am trying to edit a surface that I want to make in real life, not the topology.  The topology should be recalculated to suit my changes, not vice versa.

When lofting (in my old timer experience) the priority is:

1) Vertices

2) Tangency

3) Curvature

4) Rate of curvature

The vertices, once located, should be inviolate.  How does one make an accurate surface loft?

[Anonymous]

I am going for accurate, as much as I possibly can.  

The BD-5 is a weird little plane - the forward fuselage cross sections consist of an upper ellipse and a lower ellipse.  Same width, different heights.  Super easy to loft. 

The rear fuselage is flat sided and flat top and bottom with an increasing large radius fillet.  Different on the top and the bottom and it changes non-linearly.  The top section transitions into an ellipse forward of the vertical stabilizer.  A little harder, but also pretty easy to loft. 

Now, how to connect the two ???  Once I figure this out I'll then have to do the wing to body fairing/fillet (yikes)

[TrippyLighting]

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@Anonymous wrote:

That's the rub. I am trying to edit a surface that I want to make in real life, not the topology.  The topology should be recalculated to suit my changes, not vice versa.

When lofting (in my old timer experience) the priority is:

1) Vertices

2) Tangency

3) Curvature

4) Rate of curvature

"4" cannot be attained in Fusion 360 and even real curvature continuity "3" can sometimes be a challenge when working with surfacing tools. Mostly it works though.

For complex geometry as found on vehicle exteriors even already considering that G3 isn't attainable Fusion 360 does not have the modeling tools.

On the other hand, T-Splines are naturally G2 curvature continuous across edges, except at poles (called Star Points in T-SpLine lingo). Using the proper tools and techniques in Fusion 360, geometry can be designed that is very difficult to do with just then available surfacing tools.

From a modeling perspective, in surfacing if you start off with the wrong strategy, you'll end up often starting over from scratch. When working with T-Spines very, very rarely is that the case. Almost anything can be fixed along the way. 

Time to brush up on your "old timer" knowledge.

[Anonymous]

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From a modeling perspective, in surfacing if you start off with the wrong strategy, you'll end up often starting over from scratch. When working with T-Spines very, very rarely is that the case. Almost anything can be fixed along the way. 

Time to brush up on your "old timer" knowledge.

---

I'm happy to change my ways, I just haven't found a good strategy.  Most tutorials suggest keeping things as simple as possible and adding more complexity only when and where it's needed.  That works for pen & ink as well as CAD, so no prob there.  Maybe it's because I am trying to create a scale copy of an existing plane?  If I want to free-form a plane it's a snap.  Most of the tutorials aren't copying a fuzzy three view with cross sections for reference to the level of accuracy I'd like to get.  They are usually free forming with a few known good dimensions, or using a three view and modelling the panel lines of a sports car in 3D.  

As for old timer, I am not this old:

But I am this old:

I

Since the spline and duck days with pen & ink I've learned quite a few CAD systems, and I'd really like to make Fusion 360 sing.  I think I'm getting close!  Post some good tutorial links if you have some that would help me in this specific scenario!

[Anonymous]

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Not happy with my modelling result so far, too much oil canning, and considered going to sculpt after this....

---

 I have the same problem with oil canning when I am lofting.  I go to great pains to make sure all my control curves and rails are convex, yet my lofts always seem to have concave areas!  I'm really curious about how this happens.

[Beyondforce]

@Anonymous,

Just because you can use a certain tool, it doesn't mean you should use it. The Form is not the right tool for the job in your case! Have you watched the videos I send you?

[davebYYPCU]

Happier now, the answer for me was a single loft - not segmented sections of the fuse.

To do that there was one small fudge of the lower centreline rail, had to be made tangent, at the rear wing position.

Might help...

[TrippyLighting]

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@Anonymous wrote:

---

  They are usually free forming with a few known good dimensions, or using a three view and modelling the panel lines of a sports car in 3D.  

---

That would work for this scenario as well. I am also not advocating that Sub-D modeling is a better tool than surfacing. Both require some skill to master and both can perfectly well be used to model this particualar geometry.

Fusion 360 even allows some mixed workflows.

I created this small tutorial to contribute to a similar conversation about what would be the better tool.

It shows exactly the behavior that you describe in the title of this thread. That simply means you have to re-adjust the T-Spline or protect your existing edges with additional edge loops. Good tutorials for T-Spline models are very hard to come by and my recommendation would be to watch Sub-D modeling tutorials for vehicles for MoDo, Maya, 3DSMax, Blender, Cinema4D.