Can't Figure out lofting issue.....

[Anonymous]

Im getting this weird bubble effect from lofting with guide rails..

it is a boat hull..

I sketched the rear profile then the side profile

then lofted them together

to get the desired top profile and bends in the side of the boat i sketched them and used them as guide rails...

but some reason on the bottom of the boat it bubbles  out between the guide rail and lofted surface(the side profile of the boat)

the blue line is supposed to be straight...it is a referance of what i want the surface to be.

[mavigogun]

Export and attach your design to this thread for substantive help.

[Anonymous]

File

[davebYYPCU · Accepted solution]

You have a catch 22 happening there, the curve in the keel and Sketch 18, induce the roundness.

I got the result you want by patching that portion of the hull.  Patch the other panels, and stitch them.

Or you can replace the solid face with the face of the patch, (something I had not done before)

 

Might help...

[mavigogun]

Also disturbing is this deviation at the lower sides; notice how the surface bulges out past the Sketch element, highlit in blue.    In the process of investigating.    Likely an intended Rail wasn't selected- though it may relate to the Lofting weight, continuity selected, or selecting an Edge as Profile rather than Sketch element.

[davebYYPCU]

Selecting an edge? 

There is only one body in the file, before the mirror, created with the Loft complained about by the OP..

More likely to be level of detail settings, which are a little mysterious to me.

[TrippyLighting]

This is just a tessellation artifact in the Viewport introduced by Fusion 360's LOD (level of detail) algorithm.

Find the body in the browser, right-click on it and select "Display detail control".

Set it to "Fixed/high" and the artifacts will disappear.

[mavigogun]

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@davebYYPCU wrote:

Selecting an edge?

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Ya, given it is a solid Loft and not a Patch surface Loft, the "Edge" reference was inexplicable.

David, Peter- thanks soooooooo much for pointing to the LOD controls!    In hindsight, it is unknowable how many times I've worked to eliminate non-conforming geometry that was actually just 'sloppy' rendering for performance sake.    I'm a bit gobsmacked at the moment.    I feel compelled to scrutinize every single Loft ever executed now.

I've reviewed Preferences- is there no global control for setting default LOD?

[TrippyLighting]

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@mavigogun wrote:

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I've reviewed Preferences- is there no global control for setting default LOD?

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Nope 😉 This happens particularly in geometry with high aspect ratio.

This functionality was added in order to mainly help rendering because there the tessellation artifacts were really terrible.

Whenever such things are visible and the loft seems "off' then use the Curvature Comb, The Curvature Map and the Zebra stripe tool. If they return no bad results the geometry or better the actual mathematical representation in computer memory is OK.

[mavigogun]

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@TrippyLighting wrote:

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Nope 😉 This happens particularly in geometry with high aspect ratio.

This functionality was added in order to mainly help rendering because there the tessellation artifacts were really terrible.

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From your experience, is this a common condition/deficiency in other modelling tools- be they Autodesk products or from some other company?

[TrippyLighting]

All of the 3D CAD systems I have worked with (Solid Works, Alibre Design, Fusion 360, ZW3D) have settings somewhere, usually in the preferences, that affect viewport tessellation/quality.

In Sub-D modelers that makes littele sense because you are dealing with a mesh anyway. There you can increase the subdivision level on an object basis.

[mavigogun]

And the artifacts addressed here - unusually bad, typical, better than most?

[Anonymous]

this is unrelated... may need to start a new post... but....

how would you go about exporting a flat pattern of each panel...?

this way i could send them to a cnc table to get them cut..

[mavigogun]

Fusion generally lacks a capacity to convert curved surfaces to flat patterns- though there is limited capacity in the Sheetmetal workspace (though, I believe, not for compound curves).   Possible solutions include Meshmixer (free) and the made-to-purpose Exact Flat (paid).