3D CAD - Is there another way?

These are some thoughts on an alternative which, for some applications, maybe better than a general purpose 3D modelling system. This alternative approach maybe of interest if:

  • You don’t use 3D or only a very small subset of the 3D facilities of a CAD system
  • You've found 3D too difficult or cumbersome
  • It would take too long to define 3D geometry relative to the benefits you already achieve with 2D CAD

Problems with 3D CAD

3D is a much more specialist area than 2D CAD and no single 3D modelling system is suited to all applications. For example, a system designed to model complex doubly-curved 3D surfaces will not be able to model petro-chemical plants. However, this has not stopped some CAD vendors from trying to promote their 3D systems as being suitable for all applications. In our opinion this has never been the case and, we suspect, it may never be so.

It is surprising how similar most mid-range 3D modelling systems now are. Mid-range modellers include SolidWorks, SolidEdge, IronCAD and Inventor. As these systems run on Microsoft Windows, the user interfaces now conform to that standard. This is beneficial in that any user who is familiar with one Windows application will find a 3D CAD system that uses the same standard somewhat familiar and it will be, therefore, quicker to learn. Also most mid-range 3D CAD systems are based on one or other of the two common modelling kernels ACIS and ParaSolids. This could be a benefit if it makes the transfer of 3D geometry between systems easier and less error prone. Unfortunately there is still a long way to go before we can claim that the data transfer problems have been solved!

But why do all these 3D modelling systems have to work in the same way? Are there not other alternative approaches that can be used to create and manipulate 3D models? We believe there are, but we would not begin to suggest that the alternative outlined below is suitable for very many applications.

3D systems have become easier to use than they were 30 years ago when 3D wire frame modellers were the norm. But it is still at least an order of magnitude more difficult to work in 3D than it is in 2D. Almost the only exception are pre-prepared and well rehearsed sales demonstrations of 3D CAD systems. It’s always amusing when these demonstrations fall apart after a simple, but realistic, geometry edit is unexpectedly requested by an innocent prospective customer!

Not only are 3D systems more difficult to use, the software is also much more difficult to develop. The maths involved is extremely hard to comprehend and designing programs to handle the large volumes of calculations efficiently is very tricky. From the programmers’ point of view it is often much easier to have the user fully define everything in 3D space in a way that suits the program rather than in a way that corresponds to the user’s view of the real life objects he's trying to represent. Faced with these difficulties programmers often seem to forget that a good system should help the user rather than overloading him with unnecessary work.

General purpose mid-range 3D modelling systems may now be cheap to buy (unless you need a number of the optional extras which can cause the price to rise alarmingly). But general purpose 3D modellers are expensive to use. They are difficult and time consuming to learn and to use on anything more than trivial geometry. They also need regular practice. This is due to the nature of, and the fundamental difficulties inherent in manipulating 3D geometry. Defining 3D models parametrically only adds to the problems. As a general rule anything in 3D will take at least 4 times longer than the equivalent 2D construction, and all too often users give up after wasting hours unproductively.

3D is a fascinating area and the results can be very satisfying and is sometimes the only factor driving engineers to use 3D rather than 2D. But 3D can be a dangerous waste of time and involve a lot of pain for little real gain. This is especially so in electrical applications where the benefits of 3D are normally much less than in many mechanical engineering applications.

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Carefully implemented 3D CAD strategies can yield substantial benefits.

SpaceClaim appears to represent a significant step forward in the 3D CAD world, especially in terms of ease of use.