For more information about PBR, see other sources. The following properties are specific to PBR materials:. In Azure Remote Rendering the albedo color property is already present through the common material properties, so there is no additional base color property. Rough surfaces scatter the light in more directions than smooth surfaces, which make reflections blurry rather than sharp.
The value range is from 0. When roughness equals 0. If both a roughness value and a roughness map are supplied, the final value will be the product of the two. Conductive materials have different reflective properties, and they tend to be reflective with no albedo color.
In PBR materials, this property affects how much a surface reflects the surrounding environment. Values range from 0. When metalness is 0. When metalness is 1. For instance, if metalness is 1. If both a metalness value and a metalness map are supplied, the final value will be the product of the two. In the picture above, the sphere in the bottom-right corner looks like a real metal material, the bottom-left looks like ceramic or plastic.
The albedo color is also changing according to physical properties. With increasing roughness, the material loses reflection sharpness. Occlusion value range from 0. If a 2D texture is provided as an occlusion map, the effect is enabled and aoScale acts as a multiplier.
The opacity is defined by the albedo color's alpha channel. When enabled, a more complex rendering pipeline is invoked to draw semi-transparent surfaces. IOR input is supported in Toolbag more for scientific purposes than practical. Variances in microsurface which result in a brighter or dimmer Fresnel effect are automatically accounted for via the gloss map content.
However, there is an extra control for Fresnel for the Blinn-Phong BRDF, which is meant for legacy use as it can result in non physically accurate results. Ambient occlusion AO represents large scale occluded light and is generally baked from a 3d model. Adding AO as a separate map as opposed to baking it into the albedo and specular maps allows the shader to use it in a more intelligent way. For instance, the AO function only occludes ambient diffuse light the diffuse component of the image based lighting system in Toolbag , not direct diffuse light from dynamic lights or specular reflections of any kind.
AO should generally not be multiplied on to specular or gloss maps. Multiplying AO onto the specular map may have been a common technique in the past to reduce inappropriate reflections e. A cavity map represents small scale occluded light and is generally baked from a 3d model or a normal map. A cavity map should only contain the concave areas pits of the surface, and not the convex areas, as the cavity map is multiplied.
The content should be mostly white with darker sections to represent the recessed areas of the surface where light would get trapped. The cavity map affects both diffuse and specular from ambient and dynamic light sources.
Alternatively, a reflection occlusion map can be loaded into the cavity slot, but be sure to set the diffuse cavity value to 0 when doing this. One of the most difficult challenges when working with a PBR system is finding accurate and consistent values. There are a variety of sources for measured values on the internet, however, it can be a real pain to find a library with enough information to rely on.
Material values from most libraries tend to be measured from raw materials in laboratory conditions, of which you rarely see in real life. Factors like pureness of material, age, oxidization, and wear may cause variation in the real world reflectance value for a given object.
There are many ways to create texture content for PBR systems; the exact method you choose will depend on your personal preferences and what software you have available to you. Here is a quick recap of the method I used to create the lens above:.
First, basic materials were created in Toolbag for each surface type using a combination of tiling textures from Megascans, measured data from known materials, and where lacking appropriate reference, logic and observation, to determine the values.
Creating the base materials in Toolbag allows me to quickly adjust values and offers a very accurate preview of the end result. Often I assign base materials directly to my high poly model to get a clear idea of how the texture will come together before doing the final bakes. After setting up my base materials I brought the values and textures into Photoshop and started layering them in a logical manner.
Brass at the bottom, nickel plating, matte primer, semi-gloss textured paint, paint for the lettering, and finally the red glossy plastic. This layering setup provides an easy way to reveal the various materials below with simple masks. Similar layering functionality can be achieved with applications such as dDo , Mari and Substance Designer. After I have my base layers set up and blended together to represent various stages of wear, I added some extra details.
First I used dDo to generate a dust and dirt pass, and then I finished it off with fine surface variation in the gloss map. The exact method you use to create content for a PBR system is much less important than the end result, so feel free to experiment and figure out what works best for your needs. However, you should void tweaking materials values to look more interesting in a specific lighting environment.
We generally accomplish this as follows:. We define a base reflectivity that is approximated for most dielectric surfaces. A base reflectivity of 0. Because metallic surfaces absorb all refracted light they have no diffuse reflections and we can directly use the surface color texture as their base reflectivity.
This equation is not fully mathematically correct however. Given this, our final final reflectance equation becomes:. This equation now completely describes a physically based render model that is generally recognized as what we commonly understand as physically based rendering, or PBR. Don't worry if you didn't yet completely understand how we'll need to fit all the discussed mathematics together in code. In the next chapters, we'll explore how to utilize the reflectance equation to get much more physically plausible results in our rendered lighting and all the bits and pieces should slowly start to fit together.
With knowledge of the underlying mathematical model of PBR we'll finalize the discussion by describing how artists generally author the physical properties of a surface that we can directly feed into the PBR equations. Each of the surface parameters we need for a PBR pipeline can be defined or modeled by textures. Using textures gives us per-fragment control over how each specific surface point should react to light: whether that point is metallic, rough or smooth, or how the surface responds to different wavelengths of light.
Below you'll see a list of textures you'll frequently find in a PBR pipeline together with its visual output if supplied to a PBR renderer:. Albedo : the albedo texture specifies for each texel the color of the surface, or the base reflectivity if that texel is metallic. This is largely similar to what we've been using before as a diffuse texture, but all lighting information is extracted from the texture.
Diffuse textures often have slight shadows or darkened crevices inside the image which is something you don't want in an albedo texture; it should only contain the color or refracted absorption coefficients of the surface. Normal : the normal map texture is exactly as we've been using before in the normal mapping chapter.
The normal map allows us to specify, per fragment, a unique normal to give the illusion that a surface is bumpier than its flat counterpart. Metallic : the metallic map specifies per texel whether a texel is either metallic or it isn't.
Based on how the PBR engine is set up, artists can author metalness as either grayscale values or as binary black or white. Roughness : the roughness map specifies how rough a surface is on a per texel basis. The sampled roughness value of the roughness influences the statistical microfacet orientations of the surface. A rougher surface gets wider and blurrier reflections, while a smooth surface gets focused and clear reflections.
Some PBR engines expect a smoothness map instead of a roughness map which some artists find more intuitive. These values are then translated 1. AO : the ambient occlusion or AO map specifies an extra shadowing factor of the surface and potentially surrounding geometry. If we have a brick surface for instance, the albedo texture should have no shadowing information inside the brick's crevices.
The AO map however does specify these darkened edges as it's more difficult for light to escape. Taking ambient occlusion in account at the end of the lighting stage can significantly boost the visual quality of your scene.
Artists set and tweak these physically based input values on a per-texel basis and can base their texture values on the physical surface properties of real-world materials.
This is one of the biggest advantages of a PBR render pipeline as these physical properties of a surface remain the same, regardless of environment or lighting setup, making life easier for artists to get physically plausible results.
Surfaces authored in a PBR pipeline can easily be shared among different PBR render engines, will look correct regardless of the environment they're in, and as a result look much more natural. If you're running AdBlock, please consider whitelisting this site if you'd like to support LearnOpenGL; and no worries, I won't be mad if you don't :. For a PBR lighting model to be considered physically based, it has to satisfy the following 3 conditions don't worry, we'll get to them soon enough : Be based on the microfacet surface model.
Be energy conserving. Use a physically based BRDF. By the end of these chapters we'll have something that looks like this: Keep in mind, the topics in these chapters are rather advanced so it is advised to have a good understanding of OpenGL and shader lighting.
The microfacet model All the PBR techniques are based on the theory of microfacets. Depending on the roughness of a surface, the alignment of these tiny little mirrors can differ quite a lot: The rougher a surface is, the more chaotically aligned each microfacet will be along the surface.
In contrast, on a smooth surface the light rays are more likely to reflect in roughly the same direction, giving us smaller and sharper reflections: No surface is completely smooth on a microscopic level, but seeing as these microfacets are small enough that we can't make a distinction between them on a per-pixel basis, we statistically approximate the surface's microfacet roughness given a roughness parameter.
Together with a roughness parameter that varies between 0 and 1, we can statistically approximate the alignment of the microfacets: We can see that higher roughness values display a much larger specular reflection shape, in contrast with the smaller and sharper specular reflection shape of smooth surfaces.
Energy conservation The microfacet approximation employs a form of energy conservation : outgoing light energy should never exceed the incoming light energy excluding emissive surfaces.
The reflectance equation This brings us to something called the render equation , an elaborate equation some very smart folks out there came up with that is currently the best model we have for simulating the visuals of light.
There are a few settings for the metal exterior to achieve its grainy look, but what I want to draw your attention to is the setting of the maps. In regards to the fabric once again there are some additional textures causing the patterns but this combined with the Metallic Roughness workflow gives the appearance of material. Below are the settings that achieve this. As you would expect Roughness is at max preventing and reflectivity and because it is not metal Metallic is a nil.
To take it further if I then want to export this to Unity for instance it is really easy. I simply select export textures. Select Unity 5 Standard Metallic. It then does its thing and gives you all the textures you need in the format you need for Unity 5 Engine. Hopefully you now have an understanding of the power of PBR and realise it really is not as scary as it seems.
This is just a brief synopsis and there is a lot more that can be done with it and I encourage you to go learn and practice as it is one of my favourite parts of the 3d art creation processes.
Home About Contact Recommended Tools. Metallic Roughness The Metallic Roughness model consists of 3 channels. Base Color The base color simply that it holds all the color information and no lighting information.
Metallic This simply dictates if the material is metallic or not or somewhere in between.
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