Introduction to CAD

by leonidsurpin on May 26, 2011

Why did I decide to write this introduction?

CAD stands for Computer Aided Design.  Recently it really became a mainstay of goldsmiths, jewelers, and others involved into Jewellery Industry.  However, growing popularity of CAD have not translated into better understanding of it.  What makes matter worse is that some individuals, who are completely ignorant of the subject, are putting themselves forward as “experts”.  As a rule such “experts” invariably have a cadre of stooges, who under the guise of participants of a debate, simply regurgitate whatever comes out of the mouth of “the expert”.  Such situation makes it impossible to intelligently discuss the subject, and only adds to the confusion.  This write up hopefully will clarify some issues about the CAD.  It should enable someone with limited background to start in this field in the right way.


Shopping for CAD.

So you decided to purchase a CAD package.  How do you know which one is right for you.  There are so many on the market, and every vendor claims that his/her is the best.  You have downloaded some trial versions, but it is of little help.  So what do you do?


To be able to evaluate CAD package one must know what CAD is, so the place to start is the fundamentals of CAD.

CAD package can be simplistically subdivided into CAD engine, CAD interface, and CAD library.  Very often, in advanced packages, there are also DBMS layer ( Data Base Management Software ), but we need not to concern ourselves with it.  Industrial strength CAD packages have many components.  Still, for our purposes, we will think about CAD as comprised of 3 functional units – engine, interface, and library.

Interface is part of CAD responsible for accepting user commands, which can be in form of mouse movements, keyboard shortcuts, and in some cases as text files passed via parameter list.  Upon receiving the commands, the interface converts it to internal format and passes it to the engine for processing.  Both, the engine and the interface, make use of the library.


Most CAD packages employ the same library routines, which were developed many years ago by colleges like MIT and many others.   These routines were numerically optimized, tested over an over again.  There is no need for a user to be concern about library component.


CAD engines are different matter.  How does one test CAD engines?

There are special software packages, some in public domain, which are designed to test CAD package.  You can try to find some of them on the Web.  But even if you can’t, you can easily test it yourself.  Create a shape of high complexity.  Let’s say start with a mesh of 10000 triangles and try to manipulate it, using tools provided by interface.  If everything is fine and software responds smoothly, increase number of triangles to 100000 and see how it goes.  Eventually you will notice that software become non responsive, so you know that you have reached the limit.


Some salesmen would try to deflect it by saying that you need more memory.  Just ignore them.  You are testing different packages with the same hardware configuration.  It is true that any computer will benefit from more memory, but the task is to find out which CAD package works best on your machine.  Even badly written package can run relatively well on computer with huge memory.  We know that, don’t we?


Interface presents the most challenge for the novice.  We really have to get our hands dirty now.


Believe it or not, but CAD is very dumb software.  In it’s core it can only understand mathematically defined point.  Everything else comes from this simple concept.  What is a line ( edge is correct term ), but not 2 points.  A triangle is 3 points connected by 3 edges.  Four triangles can be assembled in pyramid, simply by making sure that  corresponding vertices coincide.  Many pyramids can be assembled into various shapes. And etc…

The same principle can be applied to many geometrical solids, which give almost unlimited possibilities of creation.


I am omitting discussion of Bezier curves, various splines, and etc…  These are mathematical descriptions of collections of points.   At the very heart of it, the point is still the king.  However some background can be helpful.  Spline is a very flexible ruler, which can be made of various materials.  It was employed by architects until the World War II, and after that in some countries.  If architect wanted to know what material can be used for a beam, a splines of different materials were subjected to loads, and their behavior was observed.

The load was provided by weights called ducks.  Getting one’s ducks in a row expression, comes from this practice.  When splines became computerized, ducks become control points.  Different materials were abstracted by different types of splines, and etc…  So do not get taken by fancy terminology.


Once you understood that, the interface can be evaluated.  Suppose you want to create a geometrical solid consisting of 1000 facets.  The question is how easy you can accomplish that.  The best case is one click of the mouse, and the worst case is to specify each and every point of each and every facet, comprising your desired shape.  Depending how well the interface under testing scores, would give you an idea of how good the whole package is.  In another words, do not just try few primitives.  All CAD packages can do it well.  Try to do something crazy and see how well your request is handled.


The very best way to start with CAD is to start with package like PovRay.

It is true that it may take you a year or more, just to get comfortable with it.

But if you master PovRay, any other CAD implementation will be a breathe.

So, in essence, you have two options.  You  can start with PovRay, which is free and only takes time to master it.  Or you can purchase a commercial package, which can run few thousand, and after investing a lot of money, you can start attending courses provided by the CAD vendor, for which you have to pay additionally.  After about a year or more, you will be at the same place, as far as knowledge of CAD, but one way will cost you only time, and another way will be the same amount of time plus a lot of money.

The choice is ultimately yours.  I do not want to create an impression that PovRay can replace industrial strength software.  It cannot.  All I am suggesting is to delay the purchase of CAD package, until you acquire the knowledge necessary to evaluate it.  And short of taking a college course, PovRay is a very good way to do it.

The website is

Manual can be seen at


Leonid  Surpin





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{ 3 comments… read them below or add one }

Suzanne June 3, 2011 at 10:40 pm

As a beginner, I have to agree with Leonid about the bombardment by “experts” with their impressive libraries. However, as Mike points out, there are other options.
I have used the MOI trial and like it. I can see that it can be conquered, unlike my experience of learning AutoCAD which defeated me. I am self teaching (no courses near me) and the online tutorials plus forum MOI offer are, for the most part, easy to follow. I can also see it as a stepping stone to Rhino.

leonidsurpin May 28, 2011 at 7:52 pm

I think there is a mis-understanding of my intentions. I was very careful avoiding mentioning any particular software, except PovRay. And PovRay has been recommended not as an industrial tool, but as a training device.

All the software mentioned above does what software suppose to do. However, it does not help a beginner to make an intelligent choice. By definition a beginner does not have the necessary background to evaluate what will be best in his/her particular situation. PovRay provides painless entry into the field of 3d modeling.

mikeedwards May 26, 2011 at 9:31 am

Wow Leonid,
You really should take a dose of your own advice and investigate the current capabilities of various software interfaces (modeling programs). I suggest you start with Rhino (A surface modeling program). It won’t even cost you anything for an evaluation copy. Get it here:
You could also also try Moi(Moment Of Inspiration) available free as a trial here:
After that you could investigate other jewelry software designed to plug into Rhino and run on top of Rhino automating common design operations (like building a shank or prong setting in cad). These plug in accessory algorithms are builders and sets of builders with extensive design libraries backing them up (Rhino gold and Gemvision’s Matrix.
After exploring surface modeling programs like rhino and Moi you can investigate a solid modeling program like 3Design, sorry i can’t find a free down load of it for you. This is only the tip of the ice berg but after that you might consider Art cam( ) or Zbrush/sculptrus:
After that you might consider joining a Cad forum or group and seek a little mentoring from other gold smiths and younger designers who are using cad. Many of these people would be quite approachable about mentoring you. In return you have much to offer them because as younger designers join the ranks of those using cad they need the experience of older bench jewelers and masters to tune their design skills to produce manufacturable cad work. You can find such a place here : You’ll need to register for full access but it’s free.
Then you can look at various cam soft wares used to prepare a cad model for manufacture like Deskproto , Rhino cam or Magics. These write tool-paths to be used in subtractive milling processes on a computer controlled milling machine or lathe or alternatively prepare a model for sterolithograghy. What I’m Getting at is that any person interested in cad has a lot more than two options and more are being produced every day. Leonid, I’ve Seen posted excepts of your video on benchtube. You’ve got great classical European fabrication skills and experience so why don’t you add a twenty first century skill to your goldsmithing design arsenal? If you’re going to continue to make claims about the best software you really need to back that up with some actual research and experience with the software in question.

Mike Edwards

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