How to make concave parts in Autocad?

Hello everyone, i kinds stuck here, how do i make a 3d model for the backrest shape as shown in the picture?

1.

i tried making a rough sketch from the front view and then adjust the vertex from SE view, but it just seems not right. it can be done but, is there any other way to make that shape easier?

using this method, i tried to sweep, but sweep can only using 1 object on a path

when using loft, only 2 objects were used when lofting it on a path.

thank you, any help is greatly appreciated.

curve and loft.dwg

Something isn't right with your drawing. Where are you getting your measurements from or are you making this up as you go along?

I didn't open your file - but someone else posted a similar problem in the past several months.

You can now project one curve onto another, so if you create 2D curve from front view and 2D curve from side view - you project these two curves to their 3D intersection curve to use as a Sweep path.

@ReMark - im just making that up because i still have no idea how to do it >

@JD Mather - ooo, so that means, we can only make that kind of shape only if we have the front and side view? or is there any other way to make it?

sorry, cant seem to reply from my office. not sure what is the problem.

For some reason your last posts needed approval by a moderator.

It also looks like the back legs, that segue into forming the main loop, have a varying thickness. Were you going to try to mimic that feature as well?

BTW...that's a bentwood hoop back chair with a cane seat. Looks like the wood might be beechwood or possibly black walnut. The chair was originally designed by Michael Thonet and carries the classic No. 14 designation.

The only dimensions I could find were these...36 5/8 x 16 15/16 x 18 3/4" (93 x 43 x 47.6 cm).

Just out of curiosity why are you attempting to model this particular chair?

i am actually trying to figure out how to make that kind of curve

from the front view, it is easy to model, but when we look from its side, the backrest have a curve, which i dont know how to do.

by figuring out the way to do this, i hope i can attempt other model, such as the skateboards, surf boards, boats and others (you know, all the sexy curve in it >

@SLW210 haha yea, thanks for approving it. really appreciate it >

You might be able to do it using a spline.

hurmm... using splines only curving it on the xy plane, the one from the picture is what i called 3d spline (i dont know what it is called).

I don't think splines care. I see no reason why a spline could not be used.

See the red arrow? It is pointing at a spline. The circle was extruded along the spline. This was done in 3D.

This was done using splines along with the Sweep command and two circles.

I did not draw the spline centerlines.

I don't think splines care. I see no reason why a spline could not be used.

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See the red arrow? It is pointing at a spline. The circle was extruded along the spline. This was done in 3D.

ahaaa, this method i already have in mind, placing a lot of points and connect it with a spline.

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This was done using splines along with the Sweep command and two circles.

I did not draw the spline centerlines.

but this one, how did you do it? mind teaching me the steps? or did you do it using the above's method? thankss

As I mentioned in post #11 I did not draw the spline centerline. I imagine it was done similar to what I demonstrated but I can't say that with 100% certainty. I can think of at least one other way it might be done without using splines but it would be rather involved.

Hurmm, ok thanks for your help, i guess i still have a lot to learn on how to make this kind of shape.

So does that mean you've given up?

nope, i will not give up until i found the way to make that shape. in fact, here is my trial n error... but its kinda.. meehhh

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this way is very time consuming if the shape is complex.

Did you draw the centerline flat then establish some vertical reference points as the basis for your shape?

yes, that is the way i do it.

i dont know any other way to do it, but i have an idea where i draw the centerline, and then draw another curve. but im not sure whether autocad can make the curve as reference curve for my centerline. i dont know what im talking about = =

Well there are many ways to accomplish a task in AutoCAD. Your job is to find the one that works best for you.

What do you mean you aren't "sure AutoCAD can make the curve as reference curve"?

If you don't know what you are talking about then there is a good chance we don't either. Try a different approach. Don't give up though. Failure still teaches us something.

JDM mentioned another approach but did not provide a link to the appropriate thread. Maybe someone else remembers the thread and can post a link to it. Just be patient.

I think I may have found the thread that JDM was referring to.

http://www.cadtutor.net/forum/showthread.php?87449-Problem-drawing-3D-object

I've yet to read through it all but when I do I'll try to point out the relative part. I'll be back.

OK...I'm back. Look at posts #11, 14, 19 and 22 as they should provide you with the necessary information. Good luck.