This is a basic tutorial on Rhino, explaining some simple functions and tips to help you :)
Note there are usually many ways to accomplish the same thing in Rhino using NURBs, this is just one way.

 I'm going to make the chair back legs in standard fashion and supporting the "back". I start with a square curve to create the cross section of this tall back piece.

I don't want it to have square, ugly edges, so I use "fillet curves" to round the corners. When done, I "Join" them into one solid curve

Next I make the curve that will define the height and bend of the back piece, it has only 3 points, which is fine, I can alter the middle one easily to change over all shape.


Now, to make the piece, I need a curve for each end, which will "flow" along the main curve to create a solid object.
For precision, I wish the to top curve to be at the same angle as the main uipright curve, rather than just cheaply squared off horizontally.
To do so, I use "Transform, Orient, Perpendicular to curve", so the curve is at 90 degree to the curve, regardless of how much the curve bends.


And here it is

Now, I connect the two end curves, flowing along the upright curve, using "Surface, Sweep to 1 Rail"


  Once I've got that done, I make a simple elongated cube, to be the horizointal support of the seat. So that it mates up neatly with the upright at the back, I boolean it, cutting it neatly. I could use "split" but that slices the end open and leaves it open, which I don't want as I wish to round the parts where the objects meat, using "chamfer", for which I need a soild object.



This is the chamfering being set. I could use "fillet" for a rounded end, but I just wish an angular, chiselled effect so I use "Chamfer" command.


And this is the result

  Next, I will make a short upright to support the front of the seat. I'm going to make this look sort of like it's been turned out on a lathe. To do this I make a curve to describe the profile of the object

And then I use "Surface, Revolve" to spin that curve in a circle, much like using a lathe.
This is the result


  Hm, it's too broad at the top, it will get in the way of the user's knee. No problem, I'll narrow just the top part of it!
Surfaces in rhino, as opposed to solids, can be deformed using "points". I turn on Control Points.

I then take the points at the top on the outer and inside edges, these define how the top is shaped., and scale them in to the middle, pulling the top into a flatter shape.

I'm going to blend the horizontal part to this ornate end, to make it look more organic. I start by making a cube object, slightly larger than the horizontal piece, then using that to "Split" the rounded end. I need it bigger, because I wish the surfaces to blendin an arc, not a straight line, so one must be bigger than the other.I also Split the end off the horizontal support using the vertical support, as blending need open surfaces, not closed solids. It's liek making a joint between two pipes using a htin sheet of steel, can't do it if it's a solid bar.

an important point in doing this is to start the initial points in a good spot, I use "snap to point" to make sure both start evenly. Then use Preview, and tweak it to it's good.

  Next I wish to make a back piece to join the sides for support and comfort. I decide I'll make a zig-zagging pipework to go with the sci-fi look. There's many ways to do this, what I did was copy the curve used to make the original upright, so I have three curves: 1 middle, 1 each side. I'm going to split them into even pieces, so I can connect curves to them, giving me a curve that follows the shape of the upright's longtitudinal curve. The ends of each split curve will give me something to attach my curve to the pipe, sort of like playing "connect the dots" ;)
I make lots of simple surfaces, then Split the 3 curves

  Next I make a curve that connects ot the end of these curves using "Osnap, End" with "Project" turned off (or it will project onto a flat plane on the floor, which I don't want, I want it to be follow the curved back)
  Once that is done, I use "Pipe" command, then I make another simple surface to split the bottom off neatly

I add a couple of shheres and scale them down in one axis, to flatten them and cover the ends of the pipe.

Now to make the seat, I am going to make a sphere, flatten it, and boolean off the ends

Flattened and scaled:

  Next I make a curve, extrude it into a surface, and use that to boolean the end off, giving a nice rounded end. I do the same to the back. With surfaces, it's important to check the direction of the UV's as that tells you which side they will boolean to, you can alter the UVs at any time with the "Dir, Flip" command"

Then I fillet the front edge to give it a more comfortable shape (just visible as thicker line at front in this shot)

Final result :)
When finished, I will often use "Solid, Extract Surface", or "Explode", to split important surfaces off an object, so they can be individually textured later on.
All original art, writing on this site, copyright of Steven James, "Silverblade the Enchanter" ©2012