[help] interpolate(t) with sweep1 not working

As seen in the photo, sweep1 works with one interpolated curve but not the other, why?

I very much prefer to be able to set a starting tangent
sweepError.gh (17.3 KB)

It’s because the start point of your rail curves (output of Join) is at the opposite end (top) from your square “station” curves at the bottom? Flip curve doesn’t fix it though… still looking… Seems to be related to using ‘Simplify’…? Weird and wacky! Restarting Rhino to regain lost preview… List of vertices (Pt param) appears to be reversed for IntCrv(t), which produces a longer line than expected. No luck yet fixing it.

Oh, wow… It appears that the ‘Te’ (Tangent End) input to IntCrv(t) has six vectors defined and internalized!? Connecting the same inputs to a fresh copy of IntCrv(t) behaves differently in that respect but Swp1 still fails. Works fine with only the other two curves joined as rails, then fails when IntCrv(t) is added. No clue why. Then again, why are you using IntCrv(t) at all? PLine seems to work fine and produce the same results? That’s an hour of time wasted that I’ll never get back. :frowning_face:

I think i’ve found the problem, but i don’t know how to fix it.
When a tangent is set for IntCrv(t) , the curve loops back on itself for some reason.
I connected a point on curve and found the point to slide back and forth when sliding from 0 to 1.
Any ideas why this is happening? / how to fix it?

this is just a portion of my grasshopper script, the list of points is generated dynamically from intersection of BBX, so sometimes the points aren’t lined up in a straight line, but curved. pline would create straight segments, which is not what i want

and sidenote, the internalised end tangents are 0’s, so it shouldn’t make any difference.

OK, but the sequence of points does appear to be significant here. The resulting line and it’s start/end points is different when they are reversed. Does it make any difference if the ‘Ts’ vectors are unitized?

after some random clicking, unitizing the start tangent solves the problem of the looping back, but still can’t sweep…