Differences between TAD and CAD (and BIM too!)

CAD or Computer Aided Drafting (Often wrongly pronounced as Computer Aided Designing — CAD does not do any designing. Only drafting) is often synonymous with AutoCAD.

TAD was written long before the current UI (User Interface) CAD standards were set.When CAD did become popular; in our little corner of the world; we were quite productive anyway — designing instead of merely drafting. Hence we never changed the UI to the so-called CAD standards.

In fact, TAD has much less learning to do and it does a huge lot with a very few set of actions that you need to learn. When TAD was conceived; the emphasis was on designing and not drafting… Drafting is a much more simpler task; once you know that the design decisions the architect took were salient and properly assessed. This influenced the nature of how the user-interface inside TAD works. The idea was to get the job of assessing design decisions really fast; and there was no emphasis on drafting.

TAD is also very different from conventional BIM software. Those are also listed below.

(This topic is being written, and many points will be added; as indeed the differences are huge)


Here are the main differences between TAD and CAD

  • CAD uses a three step thinking process to do any action:
    1. First you need to think of the shape you want
    2. Then you break down that shape in your mind and choose the creation/editing commands you want to use in CAD
    3. Then you would actually carryout that command and sit back and admire your creation The shape you had in mind indeed is now available on the screen too

TAD does not need you to think of the first step. When you create a shape – it starts off as a rectangle or a square or a triangle (depending on the initial dimensions you gave) TAD gives a placeholder shape. You can return back at your time and edit it till it forms the shape you had in mind

  • TAD simulates three persons found on a construction site. One is the architect and the other are two helpers. These virtual persons help you a lot in carrying out various actions as you create and edit your design. CAD does not have any such role-playing symbols on the screen to help you with your drafting.
  • CAD uses snap in a very different way than what happens in TAD. In CAD, there are quite a lot of ways to snap to the point you need as you keep drafting precisely. In CAD, such needs happen just-in-time i.e. as you are in the middle of some creation or editing. In TAD, you would snap the architect before you want to carry out some creation or editing action on your design
  • CAD allows all kinds of properties on graphical shapes. But if you look carefully; they are all to do with graphics: line thickness, line style, color of line and plenty more. They do make the drafted drawing look very pretty. But that does not necessarily add value to the decision making to be done by architects. TAD on the other hand can talk about a huge number of properties – so many that we gave a separate ARDELA interface for that. You can enter ANY number of properties on ANY element inside TAD but they are NOT properties concerning drafting. They are all to do with actual logical properties. You can INVENT the properties you want to note down as you go along designing.


Here are the differences between TAD and conventional BIM

  • TAD handles early stages of design quite well. You can start on a design, and may not be fully sure of the size and shapes of he rooms you plan to place in your design. Even then, you could possibly get some objective calculations going on in TAD. BIM is not very good at early stages of design
  • There are architects who think that early stages of design is to do with playing around with 3D forms This is called massing and there are some pre-BIM software that allow this (E.g. Form-it) But massing is NOT the only thing that architects do when beginning a design. TAD uses a type of programming known an loosely coupled That means the internal conceptual parts are not attached together rigidly. The architect can himself/herself decide which is the thing that is important to him/her. If it is massing, well TAD allows that too. But it also allows non-visual ways of looking into the design – Many times in India, the architect wants to know how much carpet area is getting consumed or what is the FSI (local government body calculations) that is consumed. That is all done quite fast in TAD
  • BIM gets loaded with details as you progress. This prevents iterative thinking. When a design is being fleshed out, an architect need to go around in design cycles. Each cycle ends in a criticism of what was done in that cycle. Often to get into the next design cylce; the design has to be dismantled (sometimes a bit, sometimes a lot more) and then the architect gets a better job of the next design cycle. In conventional BIM, as one works on it; it becomes heavier in no-time; and therefore to dismantle and start again design cycles is quite hard

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Last modified: le 2023/04/22 20:59