Chamfer and Fillet

Yesterday I was browsing YouTube, and came across a video about how to use some basic AutoCAD® commands, two of which were the CHAMFER and FILLET commands. Its amazing to think you could be using a basic command every day, yet still not know all of its features. But, I was impressed to see additional functionality I did not know about, and thought it was worth a post on how to get the most out of these commands.

Basic usage of CHAMFER and FILLET is as you’d expect – you invoke the command, select two lines, and a chamfer or fillet is drawn in the corner between them. Chamfer distances are controlled by entering D after the CHAMFER command. Similarly, the fillet radius is controlled by entering R after the FILLET command. If the lines do not currently meet, they will be extended to make the corner. If they are longer than required, they are trimmed back as needed. This trimming functionality can be turned off however, by entering T after either the CHAMFER or FILLET commands.

Another really useful option is to enter P after either the CHAMFER or FILLET commands. This allows you to apply a chamfer or fillet to the entire length of the polyline. Really handy for drawing roads or geometry with a standard bend radius – just draw the straight lines and use FILLET to apply standard bends to the entire length of the polyline.

Finally, I’ll point you to another article – if you haven’t already read it, give it a go. It’s a really handy way to use the CHAMFER and FILLET commands. Read about The AMAZING Fillet Zero here!

That’s all for now,


Shaped Viewports

Here’s a quick tip for today.

No doubt you’re aware that you can have custom shaped viewports – select a viewport, right click, and choose the option to clip the viewport based on a bounding object such as a polyline.

While this can be useful, be careful on drawings that contain a lot of information. There’s a reason rectangular ones are the default. Rectangles are easy for a computer to deal with. They have a set width and height, and it is easy to know what should and should not be displayed through the viewport.

Polygonal viewports are different – your computer has to mathematically determine what should and should not be displayed, and that is much more difficult to figure out for odd-shaped viewports. Incidentally, if you’re interested in how this might be done take a look at my ray casting algorithm for AutoCAD.

Therefore, where possible, try to stick to rectangular ones. That doesn’t mean use rectangular ones at all costs, just be aware that if you have a busy drawing (like a survey) and view it through a polygonal viewport, you’re in for some rendering lag!

Hope this helps,


Presenting: The HowToAutoCAD Forum’s life started at the end of 2010, and since then has grown from a newborn baby of a web-presence to — let say, a toddler. The amount of interest in my site has been fantastic, and I’m constantly getting emails and helping people around the world with AutoCAD® issues.

Whilst this is great, the only beneficiaries of these instances of support are the person I’m helping, and me. Ideally, you’d want a place to ask questions that is public, so that they can be used as a reference in the future. Also, asking questions in a public domain gives the opportunity for others to provide additional support, which helps even more. So, ideally, you’d want some kind of “forum” for this to take place…

The Forum has been born! It is now accessible from the navigation bar at the top of

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Please do come along – registration is very quick and easy, and should take you less than a minute. I’d also like to take the opportunity to encourage you to introduce yourselves in the “Say Hello!” forum, so that we can get to know who people are, where you’re from etc. And who knows, maybe in a few years I’ll give out prizes for the longest serving members of the forum ;-).

Thanks all – I’m looking forward to getting stuck into this forum!