Hi everyone,
I’m modelling a tunnel with sections. When lofting them, I experience a behavior of Rhino 7, that I not fully understand.
On the right side, the loft works as expected, the vertices on slightly different heights get connected with one edge:
Whereas on the left side, each vertex of the sections creates a separate edge:
This occurs if I loft it directly in Rhino, but also when I create the loft with Grasshopper. Why does this happen and how can I avoid this?
Thanks a lot,
Marco
Hi Marco -
I’m afraid that, based on your description and the images, I have no idea what you are asking about.
Perhaps a 3dm file could somewhat clear things up…
-wim
Hi Wim,
ok, I try it again: look at the following screenshot. On the right side, the loft creates a nice edge / seam (only one!). On the left side and on the top, it creates an edge / seam for each profile, so in the end there are lots of edges / seams.
You can replicate the behaviour with the following file: Rhino-Loft.3dm (89.6 KB)
Just select all profiles and create a loft.
If you have any further questions, just ask.
Thanks,
Marco
Well, your curves are kind of “noisy” when taken all together, turn on control points for all and look down the different rows in the tunnel direction. You can clean the surface up a bit if you use the “Refit” option with 0.01 meters - which will adjust stuff up to 1 cm - or, perhaps you don’t need nearly as many sections…
I would also separate the “floor” lines from the arch curves and loft those separately. If you want a completely ‘flat’ (planar) floor, however, you will need to adjust the control points of the arches, which are not flat/linear.
In addition to what Mitch said, you could explode the arches and loft each section separately and then join.
-wim
Hi,
thanks a lot for your inputs!
@Helvetosaur: you’re right, the curves are “noisy”. That’s because, they represent a built structure, which has some small variations / deformations. That’s also why I try solving it without refitting, otherwise we lose some accuracy.
Seperating the floor from the arch curves is a good idea, extending this by the advice of @wim solves the problem. Lofting the parts separately returns exactly the disired result!
Thanks again,
Marco
I guess the reason you were getting all the messy isocurves is that the arc segments are all of different length and angle and domain - I guess Rhino has to reconcile all of these by adding complexity. Inciodentally, I think you could easily rebuild the arc segments prior to lofting and not loose precision to an unreasonable extent - rebuilding all of the joined arcs to degree 5 and 16 points results in curves that are at most ~.001 away. 24 points is closer still, and you get away from the reational surfacre and joins etc.
-Pascal
