Seems like there should be a much easier way to use a 3d spline/polyline to accomplish the same task. In fact, I think having a 3d polyline or spline would be much better and easier to use as a baseline in a corridor than the two separate entities of alignments and profiles. I know that's how road design has been done for eons, but internally it would be so much easier to program and just do a type of sweep/loft along a path similar to how 3ds Max could do a road.
The problem with that is we typically Engineer things in the Civil world. And for that, it is by far easier to use the 2-1/2D paradigm (e.g. horizontal layout + elevation) vs. a true 3D paradigm. Artists and machinests find it easier to use the true 3D, but when it comes to a construction project, true 3D can greatly increase the complexity while not really helping.
Same thing with splines, even in 2D. They're a lot more complex a geometric figure, and make land work much more difficult. There's the raliway and highway curves, but those tend to be described in a rather simplified form that limits options, and makes it possible for computers (including calculators, data collectors, smart phones, etc.) to do those calcs with a minimum of input. Using free-form 3D splines makes for a lot more complicated possibilities, creating difficulty for everyone who must then build your design.
I think you misunderstood what I meant. I meant having the coding and such inside Civil 3D use splines or 3d polylines, but we still input the design as civil engineers have done for ages using the 2.5D paradigm. Seems like it'd just make it easier for corridor modeling if it's a spline/3dpolyline as a baseline and you sweep/loft the cross section on it. From there, extract the information you need for EOP (ETW), BOC, daylights, etc.
3D Polylines cannot have curves. And 3D splines are a more-complex geometrical figure, that cannot be labeled the way we wish in a 2.5D paradigm.
So why use 3D splines if you're already in a 2.5D paradigm? I don't see it as being "easier". In fact, I see it really complicating issues.
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