When is an approximation good enough?

[Anonymous]

(Apologies if in the wrong forum – it could go in a few!)

When is an approximation good enough?

With the recent spate of discussions generated by the Maxon Freeform plug-in, I thought it might be time to again raise a nagging question I have about ArchiCAD.


Draw a circle in 2d. You can dimension to it, accurately work out intersection points with lines etc.
Now model a 3d curved surface – for simplicity part of a cylinder.
Look at it in 3d, and you’ll see it has been “dumbed down” into facets. We all know you can increase the facet number to make it look acceptable in a rendering. But try opening a section, and all you get is facets; the geometric description of the object – that it is part of a circle, has been lost.
For rendering who cares? – I don’t. But try documenting a project and you’ll be employing lots of work arounds – drawing circles and using other overlaid 2d drawn geometries to arrive at an acceptable result.

Now it is getting messier.
You have a model that is an approximation, and 2d lines conveying the “real thing”.
Let us say you need to share your building model with a steel fabricator. However their draftspeople can draw real 3d geometries – I’ve seen their drawings (no doubt you have too) and so they need to start from scratch. Fine, it is probably best that they do from a liability standpoint (more on that later*).

However let’s say I use the freeform modeller to do a more complex shape. I can only ever convey that geometry as facets! Our steel draftsperson now only has facets to see how I arrived at the form, even if I used simple geometries and transformations (say a tilted cylinder)!

What has happened to the virtual model of the building that everyone interacts with? The concept looks a little sick if one cannot communicate the desired geometries with confidence …..

<<Aside: Revit users – can you comment on this? What happens when you section round elements? Facets? I’d love to know….>>

So how do Graphisoft get out of jail?
(*) At the moment (here in Australia at least) there is the issue of liability, and so we have the RAIA getting Architects to issue disclaimers as to the quality and use of CAD data we provide to third parties.
Hence Graphisoft’s oft touted “Virtual model” is implemented less than they might like, and we (Architects) generally encourage industry to recast our drawings rather than use what we provide, so as to shift liability.
Yes, it is inefficient.

Looking ahead.
I’ve been reading a bit about Boeing’s use of Catia on the 787 – all manufacturers use the same toolset and model. Fantastic for coordination and accuracy. Surely this is where we are headed (although given the scale of our industry maybe IFC gives us the glue to communicate together?).

So, how do Graphisoft address this? I suspect this would involve a foundation level change, but it is one that is needed ….

I’d be interested to know what you think….

[stefan]

I just returned from a conference in Lisbon and participated in a Bentley Workshop, around their new developments on "Generative Components".

Basically, this is somewhere between programming and modelling in 2D/3D. You can generate geometry based on properties and relations from other elements.

And to give an example (which is an addition on the "facetted" remarks):

1 - Assume you define a curve/spline/path, based on a few reference points.

2 - Then you put some profile on this curve, positioned every six meters.

3 - Then you assign a surface that connects this profiles.

4 - Then you "facet" this surface, but instead of putting a quad (or two triangles) on each facet, you add a real element (e.g. two connecting braces, a window element or whatever you can imagine). This "component" follows the shape of the facet, it can have some intelligence built in (e.g. skylight that orients itself to a certain direction, or a window opening that grows smaller when you are facing south etc...).

And now comes the nice part:

You, as a designer, are completely in control: you can adjust these steps at any time: e.g. move the points that define the path, adjust the profile curve, adjust the spacing between the curves, adjust the facetting, modify the "component". You can explore your own design, which simply follows your rules. You design rules, the computer derives the result.

And this is not purely for visualisation: you can flatten down the facettes so they are in a form that can be used for CNC manufacturing (e.g. laser cutters).

And remember that this is not a preprogrammed "smart" object, but a custom designed set of rules, for which you, as the designer, have control on every aspect.

This is not science fiction or academic freestyling: offices like Foster, Grimshaw, KPF and others are using these tools today as part of their practices (even when the software is not even in beta, yet). I'm not saying that this will replace CAD or BIM, but these tools can add power into the hands of the designer, right from within the design stage.

More info on: http://www.smartgeometry.org/

[Anonymous]

I read this thread and I see that you guys are in place where I was few years ago. In cad you can design everything with precision like watchmaker, but ... will carpenter make it that way ? And other thing, reconstruction of mathematical surfaces into linework. Every software I know (and I know a looot of it) is using some approximation, and conversion to facets. Some software have more control about it some less. I looked at this screenshot from revit and here is my question. If you will want to use your perspective or section view on 2D will it be constructed from mathematical splines or just lines? And the answer will be probably just lines (correct me if I'm wrong). And we are still in the same software. What will happen if we will try to convert it to other software?

[Scott Davis]

I looked at this screenshot from revit and here is my question. If you will want to use your perspective or section view on 2D will it be constructed from mathematical splines or just lines? And the answer will be probably just lines (correct me if I'm wrong). And we are still in the same software. What will happen if we will try to convert it to other software?

In Revit, each view, whether a "2d" plan view, a 3d perspective, a section, anything, including tabular (table) views....are just a view of the database. So a curve in one view is the exact same curve in another view. It's not an 'interpretation' of the curve using 2D lines, it's the actual curve. in fact, I could select that same piece in any view and change it, in turn changing the database and all other views of that piece of information.

Exporting a plan view to a DWG format will yield a 2D line drawing. Exporting a 3D view to DWG will give a 3D model.

[Anonymous]

rwallis wrote:
(Apologies if in the wrong forum – it could go in a few!)

When is an approximation good enough?


So how do Graphisoft get out of jail?
(*) At the moment (here in Australia at least) there is the issue of liability, and so we have the RAIA getting Architects to issue disclaimers as to the quality and use of CAD data we provide to third parties.
Hence Graphisoft’s oft touted “Virtual model” is implemented less than they might like, and we (Architects) generally encourage industry to recast our drawings rather than use what we provide, so as to shift liability.
Yes, it is inefficient.
I’d be interested to know what you think….

Yes its inefficient and clients dont want to pay......builders will soon go it their own way ...you only have to read our contracts and WDs...building is not an exact science...remember the carpenter working on site for $40/hr isnt interested in this crap...when your showing him the data,he wants to know why hes not earning $80/hr.....Its just getting too F****** hard....blame youselves....goodluck.

[Rob]

Yes its inefficient and clients dont want to pay......builders will soon go it their own way ...you only have to read our contracts and WDs...building is not an exact science...remember the carpenter working on site for $40/hr isnt interested in this crap...when your showing him the data,he wants to know why hes not earning $80/hr.....Its just getting too F****** hard....blame youselves....goodluck.

just note to everyone who hasn't found out yet. Do not be bothered to reply to that. it's actually software that assembles random words to some kind of sentences to stir this forum up a bit...

[Anonymous]

I've been dropping hints for a couple of years now...Your data arrays or line approximations arent worth 2 nobs of goat S***,without first collaboration and then verification..besides some builders would say,"building data isnt your business....take the hint....before its too late..."goodluck (sincerely).

[Scott Davis]

That reminds me of the movie "Airplane"....

"Jive a$$ ain't got no brains, anyhow. Sh!"