PBR Pipeline

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Physical Based Rendering is currently the best method of rendering to get beautiful realistic graphics without obliterating performance. It is good to have an understanding about what PBR is before attempting to use it. You can find a good article explaining the basics here.

The first thing to know is the engine uses the Roughness/Metal and not the Glossy/Specular pipeline. In our opinion it is the more superior option as the metal colour is stored in the Albedo map which makes it more intuitive and artist friendly, but it is important to know the difference as it does affect how your shader maps work.

Often confused with a Diffuse map, the Albedo map brings colour to your Material. This should not contain any form of shading like a diffuse map as it will reduce the overall quality of your material.

The pinnacle of 3D Low Poly rendering is the Normal Map. Using the RGB values of each pixel to calculate the XYZ distortion effect, it allows you to make a flat surface react with light sources creating the illusion of 3D in a fast-effective way. Remember that Bright uses OpenGL so the Green Channel must be inverted.

This is what allows PBR to work so beautifully. Using this very simple shader map you control how rough a surface is using a grey scale image.Remember Bright uses the Roughness/Metal Pipeline so your roughness maps work with Black being fully smooth and White being fully rough.

The metalness map is straightforward, it is a black and white image that decides which part of the texture gains a metal look to it where white is metal and black is non-metal. While it is possible to have some grey in your metalness map, it is not recommended but you can still create some good-looking materials if do you have it in there.

The Height map allows you to use the Parallax features of the pipeline. Much like a Normal map, the Height map creates a fake 3D effect by manipulates the UV co-ordinates to create a very detailed 3D surface that is in fact just a flat plane. Using this to do the larger 3D details and the Normal Map to do the smaller details is an excellent combination to create very realistic results with Low Poly models!

The reflectance map allows you to define the Fresnel Reflectance value at the normal incidence for non-metallic surfaces. Bright Engine remaps the Reflectance values of 0 to 1 from a greyscale texture to 0% to 16%. Reflectance values allow for much more realistic lighting upon specific materials such as gemstones. The following lookup table gives guidance on suitable values for varying reflectance percentages.

Reflectance Conversion Table
% 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Linear 0.25 0.35 0.43 0.5 0.56 0.61 0.66 0.71 0.75 0.79 0.83 0.87 0.90 0.94 0.97 1.0

Reflectance Values (RS) for different materials can be found in this database.

Ambient Occlusion
This adds a lot of realism by influencing how the material reacts with Global Illumination by adding darker and lighter areas of your mesh using indirect lighting. This saves a very large amount of rendering power needed as small shadows such as the underside of a plate, don't need to be calculated in real time. Ambient Occlusion really brings the scene to life but it is important not to go too crazy with it otherwise everything will start to appear much darker than they should.

This creates a fake glow effect onto your material that gives the illusion of lighting by emitting light from each texel in the Emissive map. This is perfect for small light sources such as buttons on a panel, as it is much more efficient than making lots of small dynamic lights. While the glow may look convincing it does not act as a light source so for larger light sources that you want to interact with other materials either use a dynamic light or bake it in.

The Alpha acts as a mask which tells the renderer which part of the material is transparent and which is not. While most common Alpha maps are just Black for Transparent and White for Solid, you can go into the middle ground with grey if you wanted to create semi-transparent objects like glass.

Thickness maps define how much light can pass through an objects surface when performing subsurface scattering calculations. This is a grayscale texture where white means no light can pass through therefore even with subsurface enabled, no effect will take place. Black is where all light can pass through resulting in the maximum effect. Using a variation of between these colors correctly, results in much more accurate lighting within your scene.