[cad-linux] Re: 2d vs. 3d

Hi Yorik,

seams that we have experience with very different apps. That is 
certainly useful here.

There are some architectural CADs which have some kind of 2 parts or 
workspaces.

E.g. Archicad, where you do the work on a model (you do not realize that 
usually, as you are drawing a plan, but every object has 3d properties, 
and with little effort you have both plans and model at once as a 
result. Pro: We are used to define 3d by plans with additional 
information like floor heigth etc. Contra: It only works well with 
designs that can be expressed by classical architectural plans, with 
free-forms it is getting difficult. For plot and layout, you use an 
external tool (called plotmaker).

E.g. Vectorworks, basically a 2d program, very graphical, more close to 
Illustrator than Autocad IMHO ;-) It allows to link 3d-objects to 2d 
objects. So while 2d and 3d are connected, they are not the same, and 
afaik the plans are not really generated from the model. Produces very 
nice plans, famous for contest entries. Still limited, especially if you 
want to create a form the developers did not think of.

E.g. formZ, which is more modeler, but specific for Architecture. All 
you create is geometry, a model. Than you create 2d-views from it. To 
refine these, there is an own 2d-part, something like Illustrator for 
CAD (with dimensioning, hatches and all the stuff). There is a third 
workspace, which is for layout and printing.

So there are very different approaches. I think that the difference is 
resulting mostly from the applications history, e.g. Vectorworks started 
as 2d with more and more 3d additions (compare to Autocad), while formZ 
had been explicitely designed to allow the design of new types of 
architectural forms in 3d.

I really do not worry so much about if extending a 2d app for 
architecture is so difficult. svg e.g. allows precise drawing exchange. 
An example for such an extension in a commercial app are the CAD-tools 
for Illustrator. Not much more is needed. It is more the exchange of 
data between the 2d and 3d app that is worth thinking about. Would be 
not really comfortable to reimport and work from zero after a change in 
the model, so model and drawing data should still be linked.

In fact, if we would get brlcad be useful for architecture, we would be 
much better right now...

CU Lars.

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