{"id":98,"date":"2011-05-26T01:17:24","date_gmt":"2011-05-26T01:17:24","guid":{"rendered":"http:\/\/userblogs.ganoksin.com\/leonidsurpin\/?p=98"},"modified":"2011-05-26T02:55:48","modified_gmt":"2011-05-26T02:55:48","slug":"98","status":"publish","type":"post","link":"https:\/\/userblogs.ganoksin.com\/leonidsurpin\/2011\/05\/26\/98\/","title":{"rendered":"Introduction to CAD"},"content":{"rendered":"

Why did I decide to write this introduction?<\/strong><\/p>\n

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CAD stands for Computer Aided Design.\u00a0 Recently it really became a mainstay of goldsmiths, jewelers, and others involved into Jewellery Industry.\u00a0 However, growing popularity of CAD have not translated into better understanding of it.\u00a0 What makes matter worse is that some individuals, who are completely ignorant of the subject, are putting themselves forward as \u201cexperts\u201d.\u00a0 As a rule such \u201cexperts\u201d invariably have a cadre of stooges, who under the guise of participants of a debate, simply regurgitate whatever comes out of the mouth of \u201cthe expert\u201d.\u00a0 Such situation makes it impossible to intelligently discuss the subject, and only adds to the confusion.\u00a0 This write up hopefully will clarify some issues about the CAD.\u00a0 It should enable someone with limited background to start in this field in the right way.<\/p>\n

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Shopping for CAD.<\/strong><\/p>\n

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So you decided to purchase a CAD package.\u00a0 How do you know which one is right for you.\u00a0 There are so many on the market, and every vendor claims that his\/her is the best.\u00a0 You have downloaded some trial versions, but it is of little help.\u00a0 So what do you do?<\/p>\n

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To be able to evaluate CAD package one must know what CAD is, so the place to start is the fundamentals of CAD.<\/p>\n

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CAD package can be simplistically subdivided into CAD engine, CAD interface, and CAD library.\u00a0 Very often, in advanced packages, there are also DBMS layer ( Data Base Management Software ), but we need not to concern ourselves with it.\u00a0 Industrial strength CAD packages have many components.\u00a0 Still, for our purposes, we will think about CAD as comprised of 3 functional units – engine, interface, and library.<\/p>\n

<\/strong><\/p>\n

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.\u00a0 Upon receiving the commands, the interface converts it to internal format and passes it to the engine for processing.\u00a0 Both, the engine and the interface, make use of the library.<\/p>\n

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Most CAD packages employ the same library routines, which were developed many years ago by colleges like MIT and many others. \u00a0 These routines were numerically optimized, tested over an over again.\u00a0 There is no need for a user to be concern about library component.<\/p>\n

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CAD engines are different matter.\u00a0 How does one test CAD engines?<\/p>\n

There are special software packages, some in public domain, which are designed to test CAD package.\u00a0 You can try to find some of them on the Web.\u00a0 But even if you can\u2019t, you can easily test it yourself.\u00a0 Create a shape of high complexity.\u00a0 Let\u2019s say start with a mesh of 10000 triangles and try to manipulate it, using tools provided by interface.\u00a0 If everything is fine and software responds smoothly, increase number of triangles to 100000 and see how it goes.\u00a0 Eventually you will notice that software become non responsive, so you know that you have reached the limit.<\/p>\n

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Some salesmen would try to deflect it by saying that you need more memory.\u00a0 Just ignore them.\u00a0 You are testing different packages with the same hardware configuration.\u00a0 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.\u00a0 Even badly written package can run relatively well on computer with huge memory.\u00a0 We know that, don\u2019t we?<\/p>\n

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Interface presents the most challenge for the novice.\u00a0 We really have to get our hands dirty now.<\/p>\n

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Believe it or not, but CAD is very dumb software.\u00a0 In it\u2019s core it can only understand mathematically defined point.\u00a0 Everything else comes from this simple concept.\u00a0 What is a line ( edge is correct term ), but not 2 points.\u00a0 A triangle is 3 points connected by 3 edges.\u00a0 Four triangles can be assembled in pyramid, simply by making sure that\u00a0 corresponding vertices coincide.\u00a0 Many pyramids can be assembled into various shapes. And etc…<\/p>\n

The same principle can be applied to many geometrical solids, which give almost unlimited possibilities of creation.<\/p>\n

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I am omitting discussion of Bezier curves, various splines, and etc…\u00a0 These are mathematical descriptions of collections of points. \u00a0 At the very heart of it, the point is still the king.\u00a0 However some background can be helpful.\u00a0 Spline is a very flexible ruler, which can be made of various materials.\u00a0 It was employed by architects until the World War II, and after that in some countries.\u00a0 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.<\/p>\n

The load was provided by weights called ducks.\u00a0 Getting one\u2019s ducks in a row expression, comes from this practice.\u00a0 When splines became computerized, ducks become control points.\u00a0 Different materials were abstracted by different types of splines, and etc…\u00a0 So do not get taken by fancy terminology.<\/p>\n

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Once you understood that, the interface can be evaluated.\u00a0 Suppose you want to create a geometrical solid consisting of 1000 facets.\u00a0 The question is how easy you can accomplish that.\u00a0 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.\u00a0 Depending how well the interface under testing scores, would give you an idea of how good the whole package is.\u00a0 In another words, do not just try few primitives.\u00a0 All CAD packages can do it well.\u00a0 Try to do something crazy and see how well your request is handled.<\/p>\n

<\/p>\n

The very best way to start with CAD is to start with package like PovRay.<\/p>\n

It is true that it may take you a year or more, just to get comfortable with it.<\/p>\n

But if you master PovRay, any other CAD implementation will be a breathe.<\/p>\n

So, in essence, you have two options.\u00a0 You\u00a0 can start with PovRay, which is free and only takes time to master it.\u00a0 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.\u00a0 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.<\/p>\n

The choice is ultimately yours.\u00a0 I do not want to create an impression that PovRay can replace industrial strength software.\u00a0 It cannot.\u00a0 All I am suggesting is to delay the purchase of CAD package, until you acquire the knowledge necessary to evaluate it.\u00a0 And short of taking a college course, PovRay is a very good way to do it.<\/p>\n

The website is\u00a0www.povray.org<\/a><\/p>\n

Manual can be seen at\u00a0 www.povray.org\/documentation<\/a><\/p>\n

<\/p>\n

Leonid\u00a0 Surpin<\/p>\n

<\/p>\n

www.studioarete.com<\/a><\/p>\n

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