Revit materials have evolved a lot over the last few years, reaching new levels of complexity, power and confusion. This article aims to go over some of the new concepts, common pitfalls, and tricks used to take control of your model materials.
The article will be released in three parts:
- Part 1: Three Levels of Materials
- Part 2: Common Material Problems
- Part 3: Realism and Physically Based Rendering (PBR)
Part 1: Three Levels of Materials
Sometimes, things are not as they appear. Revit splits material definitions into three parts.
- Graphic – Appearance in non-rendered graphics. This is similar to the graphic standards architects have been using in black and white drawings for hundreds of years.
- Appearance – Appearance in rendered images. This is how materials will appear once rendered. This is where you will spend the most time tweaking the material look.
- Appearance Asset – Material Appearance setting that Revit uses to find the visual appearance of a material, these can be shared across many materials. This is more of a management feature, but understanding it is crucial to avoiding complicated mistakes.
While this separation of material definitions is a powerful feature for advanced users, it is a source of confusion for many. Let’s examine how we use these material levels to our advantage.
As mentioned above, the Material Graphics tab is meant to represent materials according to architectural standards. For example bricks are often represented as a 45 degree hatch and earth has its own hatching type. These graphics are great for 2D black and white drawings where color and texture would muddle the appearance of a material for drawing documentation.
As shown above, the Graphics tab gives the ability to change a color’s “Shading” color. This can be useful to highlight a particular material in a presentation drawing, but the Graphics color has no effect on the way the material will render. So you may decide that all your welding looks bright red when you look at it in an un-rendered drawing, but it will still look like a grey metallic weld when you render it. Many users do not realize this distinction and believe that the shading color controls the color of the rendered material. This is exacerbated by the fact that Revit opens at the Graphics tab by default and that “Use Render Appearance” is not checked by default.
In reality, the rendering look of the material is determined in the “Appearance” tab, not the “Graphics” tab. To avoid ambiguity, we recommend always selecting “Use Render Appearance,” in the Graphics tab. This ensures that what you view while modeling will reflect the look of your rendered material, it is also a great way to quickly detect problems with your model’s material application. Unfortunately, there is no easy way to select “Use Render Appearance” for all your materials, it must be done manually, so it’s better to do it from the start if you plan on doing any rendering.
For instance, the images below highlights the lack of relationship between Graphic and Appearance colors. The neon colored model on the left renders perfectly fine, but there is a lot of room for miscommunication since the Graphics have no connection with the Appearances.
When the Appearance Tab uses a texture image and you select “Use Render Appearance” in the Graphics tab, Revit creates an average color of the texture image. This should result in a very close color, but in some cases, it will still be a little different than the texture image you will see at render time.
Below, we see the effect of using “Use Render Appearance” on all the materials. There is a clear relationship between the shaded representation of the model on the left and its rendered version on the right.
Keep in mind that InsiteVR uses the material definition and textures from the Appearance tab rather than the Graphics tab.
Now, lets look at the Appearance tab, where we control the actual look of the material.
The Appearance tab controls the “real” rendered look of the material. When you create a new “Generic” material you will get access to a base color, glossiness, textures, reflectivity, transparency, cutouts, self-illumination, bumps and tint.
Certain materials use “Autodesk Materials” rather than generic materials. While these materials have good intentions, they often end up limiting and confusing designers since they do not expose all the material parameters. If you do not see the typical material Appearance properties (Generic, Reflectivity, Transparency, Cutouts, etc), you can delete the material and make your own from scratch. In the next article, we will examine why Autodesk Materials should be avoided.
Material Appearance Assets
Assets are an advanced feature of Revit that require additional clarification. Assets were introduced in Revit 2013. Each asset is a collection of material properties that you can use to apply to multiple materials.
The illustration below shows which tabs in the Material Browser are controlled by Material or Asset definitions.
In our case, we will be looking specifically at material Appearance Assets. These kinds of assets include all the properties on the Appearance tab. These assets also have their own name which is different from the material they reference.
You can see the name of the Appearance Asset and if it is shared with other materials in the Material Appearance Asset information panel show above.
When you create a new material, Revit will automatically create a new Appearance Asset. Revit also lets you save and reuse these Appearance Assets through the Asset Browser.
The Asset browser also comes with a library of pre-made Assets. We do not recommend using these assets “out of the box” since many are tied to Autodesk Materials which have limited material properties, half filled material values, lackluster textures and will likely not fit any company’s naming standards. We recommend creating a company standard Material Appearance Assets library that avoids Autodesk Materials definitions, uses all required material values, your own texture images, as well as proper material and texture naming standards.
You can access the Material Asset libraries in Revit in two ways: the “Asset Browser” button or the “Replace Asset” button shown below.
You may be wondering why the definition of Material Appearances is duplicated in the Asset library. The theory is that it is possible to have multiple materials that look the same, but have different basic properties. For example, your Revit project may have an aluminum chair and aluminum studs that have the same visual look, but come from different manufacturers and have different cost and model numbers. Revit tries to alleviate this by providing you the ability to give multiple materials different identities and graphic information, but the same visual information. Revit also provides the ability to combine different Assets for Appearance, Physical and Thermal characteristics, but this is beyond the scope of this blog post.
The name of the Material Asset is located right under the Material tabs. You can change this name in the Appearance > Information section. Generally speaking, the name of the Appearance Asset Name should be the same as your Material Name.
If you do not appropriately rename your Appearance Asset names, it can create complex problems down the line (we will go further into this topic in the next article). Our recommendation is to appropriately rename Appearance Asset names for every material rather than keeping the “Generic(1)” Asset names. Establishing an office standard material library with proper naming standards will resolve a lot of these issues.
Now that you are aware of the three levels of Revit materials, you should be able to better understand why Revit materials behave the way they do. Let us know if you have any more questions in the comments.