Rounding The Edges, Chamfers And Fillets
By Neil Blevins
Created On: May 17th 2005
Updated On: Mar 13th 2008

Go here to read this tutorial in Russian.

For this lesson, we will delve into the subject of Fillets and Chamfers, and all the different techniques you can use to make them.

But first, what is a chamfer and fillet? In the pristine world of computer graphics, you have hard edges. When you make a cube, you get a sharp edge, when in real life, almost everything has a rounded edge, even if just ever so slightly. Take a look at the table below. On closer inspection, that hard edge you saw from across the room is actually chamfered. So if you want your cg to look more believable, getting those hard edges rounded is a must, it can make your work more realistic and more visually rich, since rounded edges can help pick up highlights that are otherwise unattainable by mathematically perfect corners.

A Chamfer is when you take an edge and cut it at a 45 degree angle. A Fillet is similar, but fully rounds off the edge. Take a peak at the diagrams below.

Our Base Model

Here's our base model, all straight polygonal edges. You can download the model here in obj format.

Polys, 50 faces in viewport, 50 faces in render.

We will now use every method possible to chamfer or fillet the model. Here's a list of software and methods we will be using...
• 3DStudio MAX
• Chamfer In Edit Poly
• Chamfering Multiple Times in Edit Poly
• Chamfering with Segments in Edit Poly
• Meshsmooth with Extra Loops
• Meshsmooth with Creasing
• Meshsmooth Set To Quad or Classic Method
• Meshsmooth with EdgeChEx
• Power Solids
• Round Corners In mentalray
3DStudio MAX

 Chamfer in Edit Poly First lets use 3dsmax's chamfering feature inside of the Edit Poly modifier (you can use Edit Mesh or an Editable Poly too). Apply an Edit Poly modifier to the object, select all the hard edges, and hit chamfer. Chamfered Polys, 324 faces in viewport, 324 faces in render. So this looks much better, notice the tiny highlights you're getting on those edges, it makes your model far more realistic and visually interesting. Unfortunately, the polycount has gone from 50 faces to 324 faces. However, since I performed the chamfer as part of an edit poly modifier, I can turn off the chamfering if the object is far away enough from the camera that you won't see it, or I can set the modifier to only calculate at rendertime, which will make the viewport polycount less expensive. Also, if I need to change the underlying geometry, I can get rid of my chamfering as opposed to trying to model around my chamfers. This is a really powerful feature of max's modifier stack.

 Chamfering Multiple Times in Edit Poly Similar to the regular chamfer method, except after you chamfer the edges once, you chamfer the resulting edges again. This lets you get something similar to fillet, although it adds a lot of extra faces to your mesh. It can also create some unwanted extra geometry if you're not careful, especially at corners (see below), lots of tris (3 sided faces) and 6 sided faces which is not ideal. And lastly, looking at the image below, the visual difference between your chamfer and your multiple chamfer is so slight the viewer may not notice it unless you're quite closer to your object, and hence it may not be worth doing. Chamfered Polys Multiple Times, 932 faces in viewport, 932 faces in render.

 Chamfering with Segments in Edit Poly Max 2008 adds a new feature to the regular chamfer that performs the Multiple chamfer shown above automatically. When doing the chamfer, just change the "Segments" spinner to a number above 1... Here's a closer look at the results... And here's the render... Chamfered Polys With Segments, 562 faces in viewport, 562 faces in render. This has many of the same advantages and disadvantages as the multiple chamfer method. There are a few differences though, for example 1) it's easier to apply, 2) it reduces the polycount by multi chamfering in a smarter way, and 3) The corners are also chamfered much nicer, although you'll note there are still plenty of triangles created at the corners if you look at the image above the last image.