Making use of CAD software

• to populate the terrain with buildings as easily as possible, it may make sense to leverage models and tools from the world of CAD software
• unfortunately, even today, the vast majority of CAD is only 2D blueprints, not 3D models
• conversion of 2D CAD to 3D is generally a difficult, ambiguous process requiring experienced users and lots of effort
• there are no free software tools for 3D architectural CAD - if you know of some, please tell us

CAD File Formats

• The most common formats are those that originated with AutoCAD: DXF and DWG
• DXF is a very inefficient ASCII format, generally well known and well supported, meant for exchanging files between CAD users
  • Dime is a C++ library for reading and writing DXF file data, with a strange "dual" license, GPL for use in Free software and a commercial license for commercial use.
  • dxflib is another DXF library, also with a dual GPL/commercial license
  • dxf2gl is a small, old code which loads only 3DFACE entities from DXF files
  • The DXF spec is available: a classic reference from 1988 is DXF revision 12, more recent versions (13 through 22) are at Autodesk DXF Reference
• DWG is a more compact, proprietary format
  • The OpenDWG Alliance provides a 'free' library for reading the format (although not actually "Open" - it's closed-source and has many restrictions).
  • There are a number of free viewers, and some shareware converters for DWG (e.g. IGC's DWG viewer, Any DWG DXF Converter) but there are no free converters.
• The other way to get data from CAD systems is as an explicit 3D model format, such as 3DS, although that process can lose much information.

CAD tools with support for rapid 3D construction

An excellent overview article on the pros and cons of Intelligent Architectural Modeling (AEC Magazine, September 2002)

• ArchiCAD from Graphisoft
  • complete CAD package, $4300, optional raytracing and site layout at $600 each
  • their technology hype is 'The Virtual Building', claiming that you can create one 3D model for all uses, including visualization and producing 2D construction blueprints
  • 99.6.8 received 4 sample models, in 3DS format, tried viewing them in 3DS MAX, the models look decent
• DesignWorkshop
  • $80 for "Classic", $480 for "Professional"
  • the appeal of this tool is that there are a large number of free building models (greatbuildings.com) available in its proprietary format
• AutoCAD
  • supposedly has 3D capability integrated since 2002, but presumably there's still reason to have to buy 3D Studio VIZ for full 3D visualization
• AutoCAD Plugins
  • NovaPOINT Virtual Map
    • requires AutoCAD R14 or newer
    • designed for urban environment and mapping data visualization
    • constructs a fully textured 3D scene from your CAD drawings
    • the result is viewed with their NovaPOINT Virtual Map Viewer, or can be exported to VRML
• Nemetschek Allplan FT
  • a high-end CAD package, roughly $10,000 with numerous optional modules
  • can create 3D building models with some degree of parametric control
• Revit - Parametric Building Modeler
  • $2500 + $900 "subscription", so $3400 total, with discounts for existing AutoCAD users
  • like ArchiCAD, a building modeler with high-level parametric representation for walls, windows etc.
  • the company was bought by Autodesk, so price seems to depend on your local Autodesk dealer
  • appears to be very powerful, with not only parametric architectural components, but also topographical terrain editing features (like WCS Terraffectors)
• SketchUp 3D
  • $475 for Windows and MacOSX
  • a highly parametric and reasonably priced CAD tool; tested some 3DS sample output and found some issues including lack of smooth shading on curved surfaces, mysterious units, and coplanar Z problems when loaded into OSG

Consumer drafting/CAD

• Sweet Home 3D (free)
  • Has all the basic drafting and layout features you would expect.
  • Export 3D models to OBJ.
  • Includes a large library of free 3D models, mostly for indoor objects like furniture, but also many would be useful outside as well.
  • Runs on Windows, Mac OS X, Linux and Solaris, and even has an online version for any browser supporting Java.
• 3D Home Architect® Professional 5.0 ($40, The Learning Company)
  • May 1999, evaluated version 2.1 of this software
    • pro: it's fairly easy to draw simple floor plans
    • cons: very limited palette of materials - for example, no sheetrock or gravel, does floor plans only - no structural composition of walls or roofs, but doesn't draw the actual materials, no 3D export, unstable.
  • Newer version 4.0 now has OpenGL rendering - Ordered a copy to evaluate it.
• other low-end consumer titles, which appear to be quite similar to the above package:
  • Floorplan® Plus 3D Deluxe v4.0
  • Sierra ® Complete Home® v2.0
  • Planix® Home Designer Deluxe 3D v3.10a

Historical

• AutoCAD Plugins
  • EasySite
    • $300 from Cad Easy Corp., runs only inside AutoCAD
    • semi-automatically creates roads, cul-de-sacs, landscapes, sidewalks, curbs, and houses
    • still somewhat manual modeling, but allows for very sophisticated intersections and parking lots
    • Cad Easy also now sold a version of the classic old program Facade, which turns AutoCAD floor outlines rapidly into 3D building models