Grabbing the problematic bull by the horns – developing your own add-ons

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The world of 3D design technology is an odd one sometimes, particularly in today’s web-connected world, where users are able to connect, discuss and and in some cases, whinge a bit, unlike ever before. As ever with such things, there are those that engage. There are those that make a lot of noise and seem to thrive from complaint or stirring up a fuss. There are those that are passive in their consumption of all the information out there. Then there are those that actually create something that benefits a whole community.

Personally, I’m more interested in the first and the last . A perfect example of latter, those that get off their arses and do something, came to my attention recently on twitter. Brian Hall (@QubeIt), who released a handy little add-on for Autodesk’s Inventor application that adds a couple of functions to Inventor’s rectangle sketching tools – with centre point-based creation methods at its core.

Now, the reason this caught my attention was that only the previous weekend, I’d been doing some modelling work on a little product I’ve been kicking about with for a while and came up against this exact problem. Inventor doesn’t allow you to create a rectangle from a centre point, in fact, it requires a couple more operations to create exactly that. So, Brian’s add-in came just at the right time. And it works, rather delightfully I might add.

I’d been a little frustrated with Inventor’s lack of this option (other systems have it), but what had I done about it? The answer is of course, bugger all.

As I thought about this difference, I was curious to find out why Brian hadn’t followed my passive path and become more active and actually done something to solve that frustration, not only for himself, but also anyone else (the add-in is free) – so caught up with Brian and asked a few questions.


Who are you and what do you do?

Well, I’m a late blooming CAD and programming enthusiast who genuinely enjoys solving problems in an almost obsessive way.  I’m currently an independent contractor in which all of my paid work is done for one company named Armstrong Aluminum (  In my day to day drudgery, I design aluminum framed screen enclosures that go over pools.  It’s  a very small niche industry who’s market is primarily in Florida.  I work from home on the outskirts of Orlando, FL.

How long have you been using Inventor?

I’ve been using Inventor since January 2006, starting with version R10 in a transition mode and fully converting (from AutoCAD) beginning with R11. 

What made you think about programming an add-in for Inventor?

That’s a bit of a long story, but the short version is that, while working for Armstrong Aluminum as a full time employee, my original interest in Inventor was as a platform to automate the design process for the screen enclosures I was designing.  That never came to fruition due, in large part, to the housing market collapsing (of which we are very tied to).  Once I realized that there was no money to be spent on this type of a project, I knew I would have to do it myself in my spare time, and thus began my journey to learn C# and .NET programming (circa 2009).  

Was programming something you’d done before?

In terms of writing something that someone else would use, no.

Why this project in particular?

In all honesty, I wanted to create something that would get used and beat up so that I could really test my skills.  I knew that a Center Point Rectangle is something that a lot of people have wanted for some time now so it would definitely get used.  The other two rectangle tools were just ideas that I had along the way.

Any plans for other add-ins on the horizon?

Yes, but I’m not at liberty to divulge the details… LOL, just kidding.  I have a few projects in mind.  One of them is a true Bisecting work plane tool (not to be confused with a mid-plane work plane).  That one’s a little tricky due to the inputs required to achieve a bisecting work plane but it’s doable.

If you want to see what it does, the Center Point Rectangle add-in is currently available on the rather excellent MCADForums web-site. Brian will also be writing an article for The Creative Inventor magazine, detailing the code for the add-on, so if you’re curious about how he put it together and to learn a little bit, check it out at