The Right Tools for the Job – AutoCAD Part 1

by Fenton Webb

Recently, Stephen posted this great blog entry on Performance – perception versus reality and then asked me if I could tell you all the tricks I have learnt over the years to produce the fastest, leanest AutoCAD code on the planet!!  

In fact, as Stephen mentioned in his post, I presented this exact topic at Autodesk University so I’ll present the topics inside of that presentation here in a few different blog entry parts.

So for Part 1, way before I start talking about the performance topic, let’s start with a quick look at which APIs are currently available inside of AutoCAD, along with what I consider to be their Pros and Cons…

First we have:

AutoLISP/Visual LISP… For those that don’t know, LISP is a scripting language inside of AutoCAD

Pros

• Quick and Easy to write code with
  • There is an integrated Development IDE accessed via the “VLIDE” command
• Lots of Sample Code
• Can Access all parts of the DWG file
• Runs inside of Menus/CUI Commands
  • This is extremely useful in my opinion
• Integrated Supported Language
  • It’s not going away because the AutoCAD development team use LISP in their test harnesses
• Automatic memory management
• Works same every year
  • Not affected by product changes and updates
• You can compile LISP modules
  • thus making your source code secure

Cons

• Limited ongoing investment from Autodesk
  • We are focusing more on the newer languages these days as they provide the most bang for your buck
• Limited/Outdated UI
  • All we have is the aging DCL (Dialog Control Language)
• Not easy to read and/or maintain the code
  • obviously up for discussion, but in my opinion, it’s true.
• Not Object Oriented
• Slow Performance
  • This is really task dependent. Some operations can be extremely fast though, for instance, creating objects (due to most of the work being done internally by AutoCAD)
• Limited Interoperability
  • I would say that LISP’s interoperability capabilities aren’t bad though, you can very easily interoperate with ObjectARX and .NET, and visa versa using the acedEvaluateLisp() function.
• Not a skill you can really use outside of the AutoCAD world

Next we have:

VBA…  Microsoft VBA Macros inside of AutoCAD, similar to Outlook Macros

Pros

• Quick and Easy to write code with
  • Like LISP, there is an integrated Development IDE which can be accessed via the command “VBAIDE”
• Lots of Sample Code
• Object Based
• Easy and Nice UI APIs
• Works same every year
  • Generally, not affected by product changes and updates
• Code Saved with DWG file
• Automatic Memory Management
• VBA skills are recognized outside of Autodesk

Cons

• Limited ongoing investment from Autodesk
• Slow Performance
  • task dependent, of course
• Bad Source code security
  • password encrypted macros can easily be hacked
• 64bit version runs Out of Process
  • Tricky and extremely slow
• Limited Access to AutoCAD
• No built in Interoperability

Now onto:

ObjectARX – our awesome C++ API

Pros

• Totally Interoperable!
  • Mix and match APIs
  • Not easy to implement though
• Lots of sample code
• Object Oriented
• Very powerful
  • the most powerful API we have
• Low level
  • gain access to almost anything going on inside of AutoCAD
• Fastest API we have
• Secure
  • Compiled machine code
• Advanced technology features
  • still being updated by the likes of Microsoft
• Full Access to AutoCAD
• Powerful UI API capabilities
• Recognized inside of AutoCAD world as a top notch programming skill
• Recognized outside of AutoCAD world too

Cons

• Pro software engineers needed to write it
  • Expensive!
• No built in Memory Management
• UI capabilities are powerful, but error prone and difficult
• Powerful, Low level – is this really an advantage???
  • Its power can be its downfall
• Tied to platform 32bit and 64bit
• Binary break every 3 years
  • Is affected by product changes and updates

AutoCAD .NET – our even more awesome AutoCAD .NET API

Pros

• Quick and Easy to write code with
  • VB.NET provides an easy way to port over from VBA
• Easy and Nice UI APIs
  • Built into the latest Visual Studio tools
• Totally interoperable
  • and easy with it
• Lots of sample code
• Not tied to platform
  • as long as you steer away from ObjectARX and COM interoperability
• Object Oriented
• Very powerful
• Low Level, but at the same time High level!
• Very Fast
  • but not compared with ObjectARX
• Latest and most Advanced programming language on Windows
  • New features being added all the time
• Automatic memory management
• Recognized inside of AutoCAD world as a very good programming skill
• Recognized outside of AutoCAD world too

Cons

• Code Security can be an issue, be careful
• Difficult for LISP and VBA people to migrate to pure .NET
  • Using VB.NET via COM Interop makes life easy though
• Cannot unload DLLs very easily while AutoCAD is running

Read The Right Tools for the Job – Part 2