Rhino 3D: Anything you can do I can do better!

As generally believed, there are some fine details that set Rhino apart from parametric CAD. In one aspect, Rhino can create a surface that exists mathematically, while the surface is hard to be made by an apparent set of rules in parametric modeling. Parametric CAD programs have more stringent conditions on creating a surface. If the conditions are satisfied, then the surface can be generated. If not, the surface will fail. One of the reasons for that I figure is because parametric CAD is designed for engineering and in some cases scientific applications. The 3D models or surfaces in parametric CAD must be precise and anchored on measureable parametric data. However in Rhino, it provides you with multiple ways to create a surface that is hard to defined in mathematical terms even though the surface exists mathematically.
 
Look at this example of Lofted surfaces from Rhino 5 Level 1 training manual, Exercise 59— Canoe. (The manual is here)When you prepare sketch profiles (curves) to make a lofted surface in Solidworks, the program will have to make sure the newly lofted surface go through every sketch profile (curves) with smooth curvilinear transition. It is rigidly constructed and conformed to the sketch profiles. Whereas in Rhino, you can have some other options:

 

Above are the finished Canoe and its original sketch profiles (curves)

 

In the Loft Options dialog box, the default of Style is Normal. A surface is fitted over the curves just it can be done in Solidworks.

 

 

 

 

 

 

Or, in the Loft Options dialog box, you can switch Style to Straight sections, A surface is fitted through the curves, but the sections are straight between the curves. It is much like a poly model.

 

 

 

 

 

Or, in the Loft Options dialog box, switch Style to Loose, a surface is created that uses the same control points as the curves. The surface follows the curves more loosely. Use this option when you want the surface to conform to the control points of the input curves.

 

 

 

This is an example that illustrates one of the advantages a CAD user can see in Rhino over CAD programs like Solidworks – its versatility and flexibility in getting surface made.

Quest for the strength of Rhino 3D

I have  came to know of Rhino 3D for more than 10 years. In the beginning, when it was still in its infancy, I downloaded the free trial version to play for a while. At the first sight of Rhino 3D, I was quite amazed because I thought how a NURBS modeling program can be so affordable. Back then I used Alias Studio at work to create some complex curvilinear shapes that were then hard to be modelled by Solidworks I used every day. Honestly I was a bit distasteful of Alias Studio. It was a program built on Silicon Graphics workstation and was very hard to use because it was so powerful and has so many variables that need my attention and tweaking. I was lost often in using Alias and thus quipped that learning to use Alias is like studying rocket science.

Then Rhino 3D came. It was offered as a low-cost but powerful enough NURBS modeling program under a unique business model of Robert McNeel & Associates. Though I downloaded the program to try but never paid a full attention to learn it. My company even sent me to learn it at Magnetic Visions in Brooklyn, NY in 2011. Through the training I learned the basic modeling skills in Rhino 3D, but thought that why bothering with Rhino while in Solidworks I can use hybrid of solid/surface modeling techniques to take care of most 3D modeling task.

I decided lately to dig deeper into learning Rhino and encountered several issues, which I have to get used to. The issues I have with Rhino 3D are: first of all, it is a program born out of AutoCAD era, meaning its interface bears the resemblance of CAD programs in that era. It has a command prompt window. Even though there is an alternative icon in pulldown menu to get to each command, a user still has to use command lines to get to the options under a command most of the time. Some commands are followed by the dialogue windows once selected, but only a few. Secondly, to make a sketch for modeling, the sketch normally falls on front, side, top or construction plane. This is something I have been struggling with because I am so used to parametric modeling in Solidworks where I can simply click on a plane surface to start a sketch. So far as I know, in Rhino to start a sketch it is easier to adhere the sketch to front, side, top or construction plane. Elevator Mode may be the only antidote I have found so far to break a 2D sketch away from the construction plane to which it adhere. Thirdly, Solidworks has simplified the steps of many model features that employ Boolean algorithm, for example, shelling a solid block. Shell command only becomes available since Rhino 5. Fourthly and the least is that Rhino is not a CAD program for engineers, it lacks the parametric modeling features and does not have a design feature tree that can be rolled back and forth as in Solidworks.

So that I have to bear in mind that certain modeling tasks can be done better elsewhere than in Rhino. I just have to find the strength of Rhino where other CAD programs fall short or cannot do better. Keep reading ....

Rhino 3D: 4-sided surfaces

In Rhino v5.0 training manual level 1, there is a useful exercise to compose a surface model from 6 4-sided surfaces. This manual can be found at Rhino 3D website at: https://www.rhino3d.com/download/rhino/5.0/Rhino5Level1Training

In Exercise 57 page 162 - Creating simple surfaces, 6 ways to make a 4-sided surface are demonstrated:

1. Planes:
From the Surface menu click Plane, and then click Corner to Corner.

2. To create a vertical plane:
From the Surface menu click Plane, and then click Vertical.

3. To create a plane from 3 points:
From the Surface menu click Plane, and then click 3 Points.
Beware that, in this method, SmartTrack is used to track a point from the top of the vertical plane for height of the place. When doing this, I need to turn on Object Snap (with End and Point checked) on status bar and drag the cursor to lightly touch the top corner of the vertical plane I just made in Step 2. Drag the tracking point until the surface is tilted slightly and click.

4. To create a plane from corner points:
From the Surface menu click Corner Points.

When picking the points in the next four steps, I must pick them in a clockwise direction. I tried this command and found that I can make not only 4- but 3-sided plane with this command.

5. To create a surface from planar curves:
Turn Planar mode on in status bar. Draw a curve that starts and ends at the top of the two vertical surfaces as shown below. Planar mode keeps this curve on the same plane as the surface corners.
From the Surface menu click Planar Curves.

6. To create a surface from edge curves:
From the Surface menu click Edge Curves.






This is an excellent exercise that guides me through 5 more unique ways to make 4-sided surface except the simplest rectangle plane surface. But these surfaces are still independent from one another except ever 2 surfaces share one of the 12 edges in the model. I still can move a surface by click and drag it.

I will have to use Join command to stitch them together  like this: