The purpose of this article is to answer frequently asked questions about PBR materials. If you still have questions, please leave it in the comments below!
About PBR Materials
1. What does PBR stand for?
PBR stands for "physically based rendering."
2. What are the main benefits of PBR?
By using PBR materials, you will add a more realistic quality to your renderings. These materials are impressively detailed and seamless. For example, you can distinctively see the texture of a fabric or the grain in the wood!
Additional benefits include:
- More intuitive and simpler to work with.
- More physically accurate compared to Classic materials.
- Many texture materials are readily available online.
- Importing materials is an easy drag'n drop operation away.
A lot of effort has been put into making sure textures work nicely with PBR, specially when working in the drawing and producing still images.
3. There are two different PBR workflows. Which one are we using?
The two main ways to describe PBR materials are:
- Metallic/Roughness workflow
- Specular/Glossiness workflow
We are using the Metallic/Roughness workflow due to its popularity and ease of use compared to the Specular/Glossiness workflow.
PBR Material Files
1. Are there any limitations to the resolution used for the PBR textures?
We currently have the following texture limitations:
- working in the drawing: 512x512
- producing still images: 2048x2048
There is currently no way for the user to change this. As of today, CET will reduce textures that are above 4096x4096. (The aspect will be maintained.)
2. What is the ideal resolution for textures in PBR materials?
It depends on where the material is intended to be applied.
If you are working on materials intended to be used on a floor, you need 2048x2048 since the floor will cover many pixels on the screen.
If you are working on a material used for a worksurface, 1024x1024 might be enough. But if you want to support renderings done really close to the worksurface, you maybe need 2048x2048 there too.
- Also, note that not all materials require a texture to give an excellent result. A single value may suffice for some properties, such as roughness or metallic.
The Material Lab gives you the option to reduce the resolution of the textures in the material. This can be useful if you import a very high-resolution texture for your material. Keep in mind that using higher-resolution textures will impact the render time so try to think about where the material is supposed to be used.
3. I noticed that PBR materials use .cmmips files instead of .png and .jpg. What is a .cmmips file?
Cmmips is a texture format that contains multiple resolutions for a single texture.
Instead of just storing a 1024x1024 texture, we store a chain of textures; 1x1, 2x2, 4x4 .. 1024x1024. This allows you to use a lower resolution while working in the drawing, resulting in faster snapping, drawing loading, etc. Then you can switch to a higher resolution texture when rendering.
Using PBR Materials
1. I have an 8k resolution texture. Do I have to downsample to 2k for it to work with CET's PBR materials?
Due to performance concerns, CET only allows 2K resolution textures.
Importing an 8K resolution into CET will be automatically downsampled and information and pixels will be lost. We highly recommend you downsample the textures yourselves. This allows you to have more control over what information to include in the textures.
2. Will the drawing size increase when using many PBR materials?
Yes, it may increase.
This will depend on the number of textures being used and the resolution of those textures. A PBR material supports the use of more textures compared to a Classic material. It also allows us to handle high-resolution textures efficiently.
Consequently, we should expect the drawing size to increase, but it boils down to how the extensions make use of this technology.
Our core materials are heavier in terms of memory consumption compared to before, but they are still pretty modest compared to what you could do.
3. How is the rendering time affected by PBR materials?
Since our PBR system uses .cmmips (more info above), we can choose to use lower resolution while working in the drawing. This will speed up the process of loading drawings.
4. Can you give a short introduction to all the new PBR material properties?
- The Base color property, also known as albedo, generally has the most significant impact on the appearance of a PBR material. Unlike Classic material, the base color is not supposed to carry any shadowing.
- The Opacity property defines how transparent the material is perceived. Basically, how much light that leaks through the material. You may control the opacity across the material by using a texture (also known as an alpha mask). This may be useful for creating a particular type of fabric etc.
- The normal property, also referred as bumpmap, can be used to add details to a surface that would otherwise require a lot more polygons. The texture that can describe the normal property is referred to as a normal map. There are different types of normal maps, but in CET, we expect an OpenGL-based normal map defined in tangent space.
- The roughness property defines how rough the surface is at a microscopic level. No roughness will result in a mirror-like surface, while high roughness will produce a more matte appearance. It is important to avoid mixing up roughness with the normal property.
- The metallic property naturally defines if the surface is metallic or not. Generally, it should either be 0 or 1, not in between. When a surface is metallic, the reflection color will be colored according to the base color.
- The occlusion property can be used to darken areas that light cannot reach. Generally, it is a good idea not to use it too aggressively because when we use ray tracing like we do when we are producing still images, the geometry and normal map will take care of this in a good way.
- The emissive property can be used to make the surface look as if it is emitting light. Note that, unlike other real-time (working in the drawing) renderers, CET will not produce a glowing effect around emissive surfaces.