The "extended rail" type thing would be something like this - the blend would be synchronized to each side like you've got here:



But instead of it actually stopping there, the blend would continue on with the shorter surface being implicitly extended so it would form an extended blend piece like this:



Then the extended pieces are intersected and the blend would be trimmed to form the trailing edge of the blend, like this:



I guess that seems more likely to work than trying to directly make a single surface cross section in the sharp corner...

That seems pretty tricky to attempt in an automated way, and I'll need to look at various other discontinuity cases to see how generally feasible it is... Could be something to try in v4. Probably until then a tight bend in the wing surface trailing edge rather than an actual discontinuity would probably work with Planar sections.

- Michael

Hello Michael,

I can see that extended rail Blend being very useful for a few different surfacing problems, especially if you're able to keep G1/G2 continuity between the surface and the blend itself. I'm really enjoying being able to stay in MoI more and more even for some of these surfacing operations, great job.

Here I've attached a test run of the extension technique, this one was done by actually making the wing out of an extended self-intersecting curve to start with in order to do the blends. The blend here was done in 2 separate pieces, with just regular blend not planar sections. Then it was a bit tricky to trim them, they did not intersect cleanly because of their shallow overlapping area so I had to generate an intersection curve, tweak a couple of points on it and then trim both surfaces to that common curve. Then I deleted the self-intersecting extended wing, trimmed the extensions off the self intersecting curves and then lofted those to get the final wing.

Final result is on the left, extended pieces working pieces on the right.

Seems to be a really good result, what do you think?



During some of the recent Blend overhauls I did experiment some with other ways to deal with discontinuities, without success... One attempt was to make an average of the 2 different cross section shapes at the corner and then gradually morph that back to the regular blend shapes as it travels some distance away from the corner. The problem with that is the loss of continuity in those areas.

- Michael

Hello,

The result does look very good, it looks like you've kept G2 on the wing/fuselage connection. I think I tried something similar before and trimming that trailing edge junction but I either got that weird surface flipping or problems with the trimming because the two surfaces were skimming each other. The blend issues were part of the reason I asked the question about continuity options in other tools. Having that capability puts MoI into an entirely different area of solution. I'm not complaining, but I think it would be great to have such tools within MoI, if nothing more than for MoIs legendary implementation of the features.