Best practices: Glazing in Architectural Design

Glass is an amazing material which provides a barrier from the elements while allowing a visual connection to the beauty around us; it provides light and even desired warmth in the cold season. Glass, referred to as glazing in the context of architecture, is also aesthetically pleasing in many ways, including its reflective qualities.

Traditionally, glass was challenging to represent properly in architectural visualizations. Either the color or reflections where off, or the software and settings one had to know where too complicated for the average designer. Not that they had not done it before, or where not able to learn it, but the benefit to cost of time and budget just didn’t make sense on most projects.

Thankfully, Enscape is not your father’s rendering software. This contemporary real-time and physically based rendering software is always just a click away from within your Revit, SketchUp, Rhino or ArchiCAD software. The user settings are simple: more like the controls on a camera than a spaceship. With a few simple “reflection” adjustments within the menu we can have nearly perfect glazing.

This article will cover the application of glazing within a Revit model. With the evolution of Revit materials, there are three primary ways to define glass: Generic, Glazing and now Advanced Materials in Revit 2019.

Understanding the differences between these options and how they look in Enscape is key to getting the realistic or aesthetic results you are looking for. The images above and below highlight the amazing results we can get from Enscape with just minimal effort. Not only that, but this effort is all encapsulated within the primary Revit model, not exported and refined in another format or copy of the model.

It is also helpful to know that Enscape has a material definition for glazing, i.e. classic PBR: roughness, specular (F0), metallicness, etc., and they try to map the CAD’s material system onto these. However, by contrast, in Enscape’s own material editor in SketchUp, you get the maximum control over all parameters.

As just mentioned, SketchUp has the most options for glass when it comes to Enscape because the native materials are more limiting, supporting only a texture and transparency value, and thus there is a custom Enscape Material Editor. This editor, of course, corresponds directly to the rendering engine. Sort of like Apple making an OS for its own hardware, which removes the “middle-man” and lots of guesswork and unknowns.

When dealing with glass in SketchUp the Transparency Color and Reflection Roughness are key. The smoother the material (Roughness -> 0%), the more it will reflect its environment, whereas a rougher surface will diffuse incoming light. Here is an example in SketchUp showing three different glazing conditions and their respective settings.

Notice the railing’s glass panels have a pattern. This is defined by the Texture parameter, which allows you to control the transparency using a 2D image: a map. It refers to the opacity value, so a black area (which equals zero) on the image used will result in a perfectly transparent portion of the surface, while a white area will appear perfectly opaque. Grey areas will appear partially transparent, such as glass. If you load a colored image, Enscape will automatically convert it to black and white, so you don’t have to worry about that. The image can be inverted and resized as shown here.

The Refractive Index slider determines by which factor light is being bent when traveling through a transparent surface. You know this effect from looking at a glass of water or very thick glass. Air has a refractive index of 1.0, so light rays travel through it in a straight line. Water has an index of 1.33, while the index of window glass is 1.52. Diamonds, for a further example, have an index of 2.42: they bend light quite heavily. For architectural glazing, this value can be very low or zero for efficiency. Here we see the effect when adjusting the Refractive Index on the glass panels in the railing.

As you can see, with just a few augments to the SketchUp materials in the Enscape Material Editor, some stunning results can be achieved. If you want to read more about working with materials in SketchUp, you can read this post I previously wrote: SketchUp Material Editor and Enhanced Materials in SketchUp

Using Autodesk Revit, we can also achieve amazing results in Enscape. However, Revit has multiple material shaders to reach similar results, with slight differences between them.

A Revit-provided template has the “Glass” material set to the Glazing shader option as shown in the settings below. But the Reflectance value is set quite low so the initial impact in Enscape can be disappointing at first. The range of reflectance can be seen in this comparative image, with a 100 setting on the left, 50 in the center and 0 on the right. The default in Revit is 15, which is closer to the example on the right which almost looks like there is no glass in the curtain wall system.

Revit’s advanced materials, introduced in Revit 2019, have different settings for the physically based glazing shader. It should be pointed out that this “glazing” material is different than the new advanced “glass” material. Unlike glass, light is not refracted for efficiency in glazing (as discussed in the previous SketchUp section). The result in Enscape is a surface which is always evident from any vantage point, and the reflective quality is good.

It is interesting that the new advanced material has a Visual Transmittance (T-Vis or VLT) value. Anyone specifying glazing or involved in daylight analysis or calculations will be familiar with this real-world physical property.

Revit and Insight also use this information for energy analysis. However, I am not sure if this value, in the new advanced materials, is used for that just yet. The default value shown in this example, of about 20%, is far from a normal value. In the chart below we see the range is from about 60 – 90%. I am not sure if this value effects visualization as I have not done any testing in this area yet.

Visual Transmittance values for Revit’s glazing options in energy settings (table from Autodesk Help)

Here is an example of “plain” Glass, using the advanced materials, not the new glazing option. In this case, with the darker color selected, it looks pretty good and could be used to represent a spandrel panel – i.e. non-transparent glass panels, usually used between the ceiling and the floor above on all-glass curtain wall systems like the one in this example.

The next few images show various results possible within Revit, including a patterned bump map, transmissive color adjustments, as well as tint colors. The captions offer more details for each image.

There is still much more that could be said about glass in buildings, or even in objects. But the information covered in this article should provide enough detail to achieve the beautiful results shown and additional variations by adjusting the related settings. Keep in mind, with Enscape open on a second monitor, many of these settings are visualized in real-time, making the process incredibly easy.

As glass is just an important part of architecture, it is truly exciting to see such dramatic results in a real-time rendering engine which also has a live link to our favorite 3D modeling environments.

For more inspiration, be sure to check out the Enscape Visualization Gallery to see what other customers are doing. If you have yet to give Enscape a try, download the free trial today and check it out with Revit, SketchUp, Rhino and/or ArchiCAD. If you are a student, be sure to take advantage of a free student license.