AutoCAD - Autocad 3D arc

Autocad 3D arc

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Printed Date: 16.May.2026 at 11:10

Topic: Autocad 3D arc

Posted By: Kajito
Subject: Autocad 3D arc
Date Posted: 18.May.2011 at 13:56

Hi all,

'm not completely new to 3D but came across one thing that I cannot find answer to. How do you actually draw a 3D arc? I need to model a 3D ramp to basement that consist of straight line, an arc and a straight line again (L-shaped ramp). I would normally extrude or sweep profile along a path. But I'm not able to draw the arc. I tried to draw a 2D arc and rotate it, but that doesn't really do the job.

I'm using 2006 but have access to 2012 too

Any help much appreciated.

Thanks

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English (auto-detected) » English

Replies:

Posted By: John Connor
Date Posted: 18.May.2011 at 14:33

One option using 2012 is to use the LOFT command. Another option might be to Extrude with a taper. A third approach might involve using the Slice command and Surface option. Many ways to skin a cat.

LOFT with PATH option definitely works. See image in post below. I used two profiles (one for each end).

-------------
"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>

Posted By: Vladimir Michl
Date Posted: 18.May.2011 at 14:37

Arc is always 2D - but you can draw it in any workplane - so first define a UCS in 3D and then draw an arc in it. The proposed way of using 3DROTATE to rotate an existing "flat" arc also works.

-------------
Vladimir Michl (moderator)
ARKANCE - https://arkance.world" rel="nofollow - https://arkance.world - Autodesk Platinum Partner

Posted By: John Connor
Date Posted: 18.May.2011 at 15:05

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"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>

Posted By: Kajito
Date Posted: 18.May.2011 at 16:31

'm sorry guys, I forgot to mention that the ramp is an access ramp between basement and ground floor. That's why the loft command is not really working because I dont have the path. One interesting thing is that when I draw an arc and then rotate it in 3D, I cannot trace a 3D polyline on the arc. I'm really confused about this one.

How do you actually draw 3D curve?

English (auto-detected) » English

Posted By: John Connor
Date Posted: 18.May.2011 at 17:04

What information do you actually have? Do you have...

1. The height difference between the basement and ground floor?
2. A layout for both floors for siting purposes?
3. A predetermined width for the ramp?
4. A site plan?

This is an exterior ramp? Yes/No?

-------------
"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>

Posted By: Kajito
Date Posted: 18.May.2011 at 17:33

John,

I have it all: 3.5m difference between floors (sfl), ramp profile (rectangular slab with kerbs), both plans. It is just a classic ramp within a building for an underground car park. (The building itself is finished but I'm doing some 3D models for presentation purposes). It should be easy, but somehow it is not. I can do it without issus in one plane or on straight line, but when it comes to the curved 3D Part it doesn't work. I have a feeling I'm doing some basic stupid mistake.

English (auto-detected) » English

Posted By: John Connor
Date Posted: 18.May.2011 at 19:06

Maybe you can use a helix and slice off what you don't need. Or maybe use a spline?

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"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>

Posted By: John Connor
Date Posted: 18.May.2011 at 19:53

It can be done using the LOFT command but first you'll have to create your "Guides" with a Spline. I tested it and it does work. Some attention to detail is required when placing the pick points for your splines (you'll need two, one for each side of the ramp).

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"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>

Posted By: John Connor
Date Posted: 18.May.2011 at 20:01

Curved 3D ramp.

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"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>

Posted By: Kajito
Date Posted: 18.May.2011 at 23:17

thanks for suggestion John. my issues is not with the loft or anything such as, but with the guides/paths. Spline works fine but it is not the exact geometry (althought it is only for presentation I'd like to know how to make it right). it will not create straight line, arc as tangent and straight line again. (or am I missing smth).

I tired the helix but i honestly cannot get my head around, it is the first time I used it to be honest.

Posted By: John Connor
Date Posted: 18.May.2011 at 23:36

You must be using a different "spline" than I am because as you see from my last image I have a straight section followed by a curve followed by another straight section.

I think if you use a helix you would have a lot of slicing to do. I threw that out there before I had a chance to test the spline option.

-------------
"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>

Posted By: Kajito
Date Posted: 20.May.2011 at 10:56

John,

yeah the spline actually works fine, dont know why I thought spline cannot have a infinite curvature ... my brain doesnt seem to work these days ;))

thanks for help

c u at next topic ;)

English (auto-detected) » English

Posted By: John Connor
Date Posted: 20.May.2011 at 12:41

Well it seems we both learned something. I'd call that a win-win. You're welcomed Kajito.

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"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

<<AutoCAD 2015>>