[BUG] loft tool broken!

[TrippyLighting]

I tried to help the user in this thread but the tool so utterly fails in so many way it is really quite exasperating.

Failure #1 :

As can be seen in the screencast in that thread, the  loft tool does not compete the closed loft. It warns about self intersection, but geometrically there should not be any.

Failure #2:

Also, when I change from "Cut" to "New body", instead of just assuming that bodies color it turns yellow to indicate intersection.

So the second time around I create a plane on path along the outer rim and then 2 sketches to provide the loft tool two non-coplanar loft profiles to loft through. The results are devastating.

Failure #3

When selecting the profiles first and then selecting "closed" without a rail to guide it yet, the loft preview naturally intersects the body. As can be seen I am having a terrible time just selecting an edge and while I have "chain selection" enabled, the tool only selects the chain up to the point where the loft preview intersects the body. But somehow I succeed at some point in time.

Failure #4 the preview then shows a cut loft in red, but when I change it to new body, the tool deselects the rail.

And Oh what joy, now I can also get the tool to reliably crash so I am calling for reinforcements @Phil.E:

CER_182158961

Model is attached.

[jeff_strater]

A few comments:

1. Closed loft with only two profiles is ambiguous.  What looks like is happening is that the close actually back-tracks along the initial path (hence the self-intersection).  I think technically that "closed" should be disabled unless there are 3 or more profiles.  
2. the wrong action when switching to "new body" is a bug, clearly
3. the workflow in the second video.  The reason that chain selection doesn't work is because of the preview.  The preview is actually acting on the body, so the edge is not really there in its full length.  I found that if I switch the operation type to "new body" before selecting the centerline, it works fine:

1. the crash we have been able to reproduce, and will look into that

[TrippyLighting]

Well ... I also thought that might be the case, which is the reason I provided the tool with 2 more profiles with reported undesirable results 😉

If, however, ambiguity with 2 co-planar loft profiles is the culprit, then I'd love to hear your explanation why the workaround I provided in the thread I linked to above works.

I simply took the edge and 3D projected it into a separate sketch.

Then 2 co-planar loft profiles were not problem whatsoever, chain selection worked and creating this loft was not problem whatsoever. It just does not work with the body edge(s) directly.

[lucasproko]

Hey @TrippyLighting,

I think you might have misinterpreted Jeff's response just a bit. It's not that 2 co-planar lofts is creating this problem, it's that closed lofts don't work properly with only 2 profiles. Also impacting this issue, is that if you select the Centerline while the Operation is still set to Cut, the command is having a hard time building the Centerline because the Previewed-Cut-Operation is breaking up the continuity of the edge loop. In Jeff's screencast, you'll notice that switching to New Body before choosing the Centerline allows this to build properly. 

Hopefully you understand now what's going on underneath the hood, but there's still obviously room for improvement in the following areas:

1. Fix the crash when de-selecting the second Profile
2. Block the selection of "Closed" unless there are more than two profiles selected
3. Improve the ability to use model edges as rails even if the edges are altered throughout the operation

Let me know if you have any questions on this, or if you have any further suggestions.

Thanks

[TrippyLighting]

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@lucasproko wrote:

Hey @TrippyLighting,

 it's that closed lofts don't work properly with only 2 profiles.
 

 So does this video debunk that statement ?

😉

Also, please be aware that this whole modeling method could already be considered a workaround. 

What the user in this thread is trying to do is to 

[lucasproko]

@TrippyLighting - 

Yes, your video shows that you can create a closed Loft using only two profiles, but you need to have a centerline that touches both for that to work and that is typically not the case. For instance, the first situation is much more common than the second in the below screenshots:

Closed does nothing hereBut here it does

I should have been more explicit and also said to block the "Closed" checkbox unless there are more than two profiles or there is a centerline that touches both profiles.

Regardless, the point I was trying to make was that it does not matter whether the two profiles are co-planar or not. The issue is that the edge selected as the centerline is being destructed as a part of the operation which is resulting in un-intuitive results. Given that, either pre-selecting New Body before selecting the Centerline, or projecting the 3D edges are the best workarounds for now.

[richard.hallT2EK9 · Accepted solution]

Hi Peter, I believe that almost all of the issues you have raised here have been addressed now. The only one remaining (as far as I am aware) is the ability to select the centerline once a cut/join operation has been previewed .. this can currently be circumvented by pre-selecting that piece of topology. I have remedied, and added tests for the closure issue, the operation cycling of 'Cut', 'Join', 'Intersect' and 'New Body', and the selection problems. Many thanks again for this useful example as it has highlighted many errors, and hence been great in helping make the lofting tool a lot more robust.

[TrippyLighting]

Hi Richard, thanks for the feedback!

[richard.hallT2EK9]

My pleasure .. thanks again for your help.