II: Projective Geometry in a CAD Program

From: Jonathan Chertok (chertok22@hotmail.com)
Date: Wed Apr 09 2003 - 23:51:32 EEST

Charles and List,

It's very encouraging to get the lists experience, suggestions and referrals.

I have two goals:

1. I plan to sit down as an exercise to recreate some old plates on Projective Geometry in the computer. The idea is to get a scanned raster into CAD (finished) and then to do the exercises described by the plates in "actual" 3D in the computer.  These are all from Gaspar Monge's Projective Geometry , and is basically a continuation of my Graduate Architecture research. For this I need a "snap to plane", "rotate about plane" and - I am sure - a number of other operations that I have not thought about.

So far it sounds like Rhino would be the best bet for this.

2. I spent some considerable time in ACAD 2000 drawing an architectural project that was generated from a 3D form. This means that I generated the shape in a small "sketch model", rationalized it according to a reasonable geometry, entered a wireframe into the computer - and sort of went back and forth between 2D and 3D in a somewhat herky-jerky manner.

AUTOCAD has a couple great features called "Wblock" and "Xref'. These allow one to pull specific information out of a drawing, throw it into a file, and then reference that file in other drawings. I spent a lot of time trying to figure a way to pull "points" or "nodes" out of my 3D wireframe model in order to "throw" that information into a 2D drawing - from which I could draw a conventional building section.  ** It would be nice to have been able to update the wireframe models - update the "points" or "nodes" in the changed sections for the wireframe - and to then go into the 2D sections and update those 2D drawings in order to accomodate the changed geometry...does this make sense?!

I think I only need this in the 3D and 2D Drafting sense (in that I think I could create an RP ready model as a separate file and not need to involve a presentation or process model in the more conventional drafting process).

Obviously, I realize that there is a lot of territory that can be covered between the conventional idea of an architectural drawing and RP and NC/CNC Fabrication Techniques. Currently I have been looking at the Yokohama Port Terminal by Farshid and Moussavi, as well as Kansai International Airport by Renzo Piano.

Is anybody familiar with CATIA (or perhaps Mechanical Desktop). I'd love to get a CATIA "development licence" (think benevolent corporation helps talented young architect - anybody with some pull listening?) - - but in the meantime am wondering if there is a way for me to further my architectural research (with another program) and was hoping someone in the list knew of an appropriate step between ACAD and CATIA.

Thanks Very Much,


Universal Join
t Design Build
Full Service Design and Construction
Jonathan Chertok. Principal
Austin Texas [512] 407 9628
Buildings + Digital Manufacturing

>From: "Charles Overy"
>To: "Jonathan Chertok" , "Rapid Prototyping"
>Subject: RE: Projective Geometry in a CAD Program
>Date: Wed, 9 Apr 2003 11:54:48 -0600
>Sounds like you are looking for a 3D architectural CAD program that actually
>works the way architects do? None of those.
>Seriously though, one of the things that you may have to define first is if
>you intent is to create RP, or is it to draw in 3d in the manner that you
>would like and then deal with the possible prototypablity latter. I think
>this will influence your choices.
>We do some of what you describe routinely in FormZ although it is not
>usually simple to set up. We have also received autocad files that are set
>up the way you describe. Again, it appears not to be trivial and, if you are
>going out of autocad to RP you are pretty stuck as you will need a 3rd party
>plug in to get more than one solid object out at a time as .stl(at least in
>2000, architectural). In both of these programs you will also need to draw
>your building using solids if you intend to RP. On the Rhino front, we have
>one person in our shop who prefers Rhino most of the time but he
>occasionally misses the flexibility to point edit forms that Form Z
>provides. As far as the derivation of 2D, I can oly speak for Form Z, where
>it is easy, you just render as a hidden line drawing. There was also a post
>to the list recently about a tool that was specifically directed at
>generating 2D working drawings from .stl. I cannot recall what it is but
>someone else might.
>On the non solid, simple side, a great many people are having sucess with
>Sketch Up. This is a quick architectural sketching modeler. It does do
>imports but I have not seen it used in the projection manner you describe.
>Also it is a planar modeler, no solids. However, we have sucessfully
>resurfaced sketchup data with our new polygonmesh resurfacer and can create
>buildable stl files from this data.
>Revit is the on again off again hot new architectural modeler. I have used
>it a bit but when the got purchased by Autodesk they cut our development
>license off. We had a good relationship with them prior. Again no RP output,
>you would have to go out through 3DS or DWG/DXF and at last release the
>polygon mesh was highly degenerative. Basically, like ACad they are not too
>interested in interoperability. They can do most of what you say but again,
>it is not a sketch tool, it is a full parametric CAD modeler
>Off all of your requirements the section is one of the more ineresting. You
>can do this in Form Z but it is not easy. As far as I know you have to cut a
>section with a plane or object through each and or all 3d objects. I would
>imagine you are looking for a section "slider" interface, x,y,z etc., like
>the ones that are very prevalent in RP preprocessing middleware. I have not
>seen this useful interface in any architectural CAD but I have not looked
>for it extensively. Revit will allow you to position and then operate on a
>section view through the 3D model so it is closest that I know of.
>We are actively evaluating Nemetscheck's Vectorworks Architect but are not
>very far along yet.
>Please let me know the results of your search and if you find other resouces
>in you investigation. If Makai Smith and Kevin Rotheroe do not respond on or
>off the list you may want to ask them their thoughts directly as they are
>gurus of Architecture. Also I am working on a CAD/technology in
>architecture resources like Jerry Laiserin's www.laiserin.com . I
>appreciate any links.
>Very Best,
>-----Original Message-----
>From: owner-rp-ml@rapid.lpt.fi [mailto:owner-rp-ml@rapid.lpt.fi]On Behalf Of
>Jonathan Chertok
>Sent: Tuesday, April 08, 2003 6:23 PM
>To: rp-ml@rapid.lpt.fi
>Subject: Projective Geometry in a CAD Program
> A. Does anyone know of a CAD program within which one can conveniently do
>"projective geometry".
> I am hoping for a 3D program within which I can set up a couple of
>"planes" in order to project lines to create a 3D object from a series of
>elevations - or to create a series of elevations from a 3D object. I suppose
>an ability to snap to a plane and to create a perpendicular to this line
>would be useful.
> B. Similarly, I am wondering if there is a program within which one might
>have a command "Project Outline" or "Find Points in this Section" which
>would yield information in the form of points or lines from which I could
>construct additional drawings.
> Here I am hoping for a 3D program which would allow me to construct a 3D
>shape - take sections or elevations of it - and then construct additional
>drawings using this "section" or "outline" information.
> I have tried this in ACAD 2000 but after a lot of noodling around it
>seemed rather unsatisfactory for my needs.
> Thanks,
> Jonathan Chertok
> Universal Joint Design Build
> Full Service Design and Construction
> Jonathan Chertok. Principal
> Austin Texas [512] 407 9628
> Buildings + Digital Manufacturing
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