Through the Interface

Free webcast: "AutoCAD: .NET for LISP Programmers"

On October 18th we're delivering a free AutoCAD development-oriented webcast entitled "AutoCAD: .NET for LISP Programmers". Check here for our overall API schedule, or go here to register directly. These sessions are typically held at the end of the working day in Europe (5pm CEST) which is the beginning of the day on the West Coast of the US (8am PDT). As usual, I'll post a link to the recording, once it's available. Read more →

Loading the right version of an ObjectARX module into 32- or 64-bit AutoCAD

This question has come in from a number of developers... How can I tell when my application is running inside a 64-bit version of AutoCAD? As mentioned in this previous post, AutoCAD 2008 installs as native 64-bit binaries on a supported 64-bit OS, just as 32-bit binaries get installed on a supported 32-bit OS. A minor complication is that certain of our AutoCAD-based products do not yet have native 64-bit versions. Our Engineering teams are working on this, but in the meantime, your application might well be working inside a 32-bit Autodesk product on a 64-bit OS. So how... Read more →

Protecting intellectual property in AutoCAD application modules

This is an interesting topic – and one that I’m far from being expert in – so it would be great if readers could submit comments with additional information. Intellectual property protection is a major concern for software developers, and issues that are seen today with .NET languages have been troubling AutoCAD developers since the introduction of AutoLISP. So, what are these issues? As a professional software developer, if you ship source-code to your customers there is substantial risk of it being borrowed or stolen for use in other unlicensed situations. This is true if you ship the actual... Read more →

Linking Circles, Part 5: Animating the snake

As promised in the last post, here's some old LISP code I used to demo the original circle linking application. I've changed it slightly to not only move the snake in 2D, now the Z-value of the lead object is set to be a fraction of the object's Y-value. This won't actually change what's seen in a standard overhead view... if you want to revert to 2D-only movement of the snake, simply remove "zval" from the two calls to the MOVE command. I should also add that while the snake will move through 3D by default, I didn't change... Read more →

Controlling interactive polyline creation - Part 1

I received this interesting question through by email over the weekend: “How can I ask AutoCAD to let the user to draw a Polyline (just like the user pushed Polyline button) and then just after finishing drawing get the ObjectID of that entity? Is it possible?” This is a fun one, as there are a number of different approaches to take. I’m going to outline (or just go ahead and implement, depending on the complexity) the various possibilities – taking the first two today and the others in (a) subsequent post(s). The idea is to define our own command,... Read more →

Passing arguments to .NET-defined commands

Another case of planets aligning: two different people have asked me this question in two days... It's quite common for commands to require users to provide additional input during execution. This information might be passed in via a script or a (command) from LISP, or it may simply be typed manually or pasted in by the user. The fact is, though, that commands don't actually take arguments. It may seem like they do, but they don't. What they do is ask for user input using dialogs or the command-line. Here are a few tips on how to support passing... Read more →

Calling DIMARC from Visual LISP

This is an interesting little problem that came in from Japan last week. Basically the issue is understanding how to call the DIMARC command programmatically from LISP using (command). The DIMARC command was introduced in AutoCAD 2006 to dimension the length of arcs or polyline arc segments. What's interesting about this problem is that it highlights different aspects of entity selection in LISP. Firstly, let's take a look at the DIMARC command (I've put the keyboard-entered text in red below): Command: DIMARC Select arc or polyline arc segment: Specify arc length dimension location, or [Mtext/Text/Angle/Partial/Leader]: Dimension text = 10.6887... Read more →

Handling Automation errors in Visual LISP

Since Visual LISP was introduced, developers have taken advantage of its ability to call COM Automation interfaces (whether AutoCAD's or other applications'). The addition of this functionality to the LISP platform created many new development possibilities - previously you were able to call through to ObjectARX applications defining LISP functions, but enabling Automation access from LISP suddenly allowed developers to access any other application adopting the COM standard its API, such as Microsoft Excel. A quick note on error handling in LISP... Traditionally LISP applications have defined their own (*error*) function to trap errors during execution. During this function... Read more →

Techniques for calling AutoCAD commands programmatically

It's quite common to want to call commands from one or other of AutoCAD's programming environments. While it's cleanest (from a purist's perspective) to use an API to perform the task you want, the quickest way - and the one which will appeal to the pragmatists (and the lazy) among us is often to call a sequence of commands. And there are, of course, a few places in AutoCAD where APIs have not been exposed, so scripting commands is the only way to achieve what you want. Let's take the simple example of adding a line. Here's what you'd... Read more →

Breathing fresh life into LISP applications with a modern GUI

This recent entry on Jimmy Bergmark's JTB World Blog brought to my attention the fact that ObjectDCL is about to become an Open Source project. Chad Wanless, the father of ObjectDCL, was a very active ADN member for many years, but - according to this post on the ObjectARX discussion group - is now unable to spend time working on ObjectDCL due to a severe medical condition. In case Chad is reading this... Chad - all of us here at ADN wish you a speedy recovery and all the best for your future endeavours. Ignoring the background behind the... Read more →