A short guide to glass – Part 1

Today I want to talk about glass and how glass is perceived in our real world and how we can properly create glass in 3D visualization. In everyday life and in our real environment, we generally give little thought to the composition of individual materials and how they interact with light. Since I’ve been working even more intensively with architectural visualization than before, I personally pay even more attention to materials, surfaces and their properties. When it comes to glass, I would say that many people have a very simple approach when it comes to glass design. A lot of people think that if the material is primarily transparent and reflective, then it’s probably glass and everything else will be covered and taken care of by the render engine. Don’t get me wrong, when I started my career in 3D, I was of the same opinion and simply didn’t know any better. But over the years, I’ve thought a lot about the „whys“ and „wherefores“ and not just focusing on the modeling or creation process. Since my first forays into 3D, I’ve always tried to achieve the most realistic results that are as close to reality as possible. Of course, to be fair, I have to say that I didn’t fall from the sky as a master, it took long and hard years of learning to achieve what I know today, and that’s not much. Even today, I still learn something new every day and sometimes it seems to me that the past few years were just elementary school.

But enough of the introduction, let’s move on to the actual topic and explore the wonderful world of glass together.

The first thing I’ve always noticed is that the thicker the glass, the greener it appears. At first I thought that green color pigments were simply added during production to achieve this effect. But that would have been too simplistic, so I did some research some time ago and read a lot about it. You usually only notice this „green fringe effect“ the steeper the viewing angle. You might think that this has something to do with „optical illusion“, but in fact this green tint is caused by the presence of iron oxide in the glass itself. Another point is the „index of refraction“, also known in 3D as the „IOR – Index of Refraction“. The higher the value, the more pronounced this effect is; the lower the value, the less pronounced this green cast appears.

Incidentally, there are several pages on the internet where you can find various lists with the correct refractive index values of individual materials. You can find one such list here: https://pixelandpoly.com/ior.html

So that we can create the right glass shader together step by step, we now switch to Blender. I would prefer to do it in 3ds Max and VRay, but since Blender is very fashionable at the moment, I’ll show it in Blender and Cycles.

There are basically three different approaches to creating a glass material in Blender. The old method, the existing method and the extra method.

Next, we want to briefly color the glass a little and what I see very often in videos or posts is that many simply change the „base color“ for this. You can do this, but it’s not very effective and it’s also wrong. In this short video, I first show the wrong way and then a possible correct approach.

The next step is about the beam depth, one of the reasons why the glass looks more realistic in Octane is the well-tuned beam depth. In Cycles the default value is fundamentally wrong and why this hasn’t been changed long ago is a mystery to me. Pay attention to the glass material when I increase the values, just increasing the beam depth in the „light path area“ makes the glass material look much more realistic and natural.

When it comes to glass, we mustn’t forget the caustics and the default values in Cycles are quite unnatural. Let’s see what we can achieve if I correct a few more settings for this. I would also like to mention that these values are not the norm, but must be subtly adjusted depending on the scene and object as well as the lighting conditions. Individually, they may only be very small changes, but together they result in a natural look.

Well, we’ve finished the first part for today, but there will be more episodes and I hope this first part has whetted your appetite for more.