PBR in UE/Unreal Engine

1. Relevant parameters in UE-PBR material

1. Lighting

• Direct light highlights (direct-specular)

• Indirect light highlights (indirect-specular)

• direct-diffuse

• Indirect light diffusion (indirect-diffuse)

• Shadow + Ambient Occlusion (shadow+AO)

2. Surface properties

• base color

• Metallic

• roughness

• Highlight (specular)

• normal

2. The principle of light generation

 

1. Direct-specular

• Illumination comes from direct light;

• Reflections will be concentrated in one direction, producing highlights;

• The effect is as shown in the figure:

   

2. Indirect light highlights (indirect-specular)

• Lighting comes from reflected light from all objects in the environment;

• The divergence of the light source causes the highlights to also diverge;

• The effect is as shown in the figure:

   

3. Direct-diffuse

• The light source comes from direct light;

• reflections in all directions;

• The effect is as shown in the figure:

   

4. Indirect light diffusion (indirect-diffuse)

• The light source comes from the reflected light of all objects in the environment;

• reflections in all directions;

• The effect is as shown in the figure:

   

3. Analysis of surface properties

1, base color

• Intrinsic color is a plane map that does not contain lighting information;

• In reality, there are almost no pure white and pure black objects of intrinsic color;

• material	Intrinsic color strength
  charcoal	0.02
  green grass	0.21
  fresh concrete	0.51
  white snow	0.81

• Intrinsic color map:

   

2. Metallic

• The degree of metal, the value is between 0-1, the effect is as shown in the figure below;

• The default value in UE is 0;

• The reason for the color of the metal degree: when the metal degree is 1, the reflection degree is 100%; 

• Reflectance: When the reflectance is 0%, it is pure diffusion, and the color appears as the intrinsic color; when the reflectance is 50%, the color appears as 50% of the intrinsic color diffusion + 50% reflection; when the reflectance is 100%, the color appears It is a pure reflection, and the color is rendered as a multiplication of the reflected color and the intrinsic color;

• 

   

• Metalness map: The material is usually metal or non-metal, so the metalness map is usually either black or white, and the contrast is very strong;

3. Roughness

• The degree of smoothness, the value is between 0-1, the effect is as follows:

• 

   

• Roughness map:

   

4. Specular

• The highlight affects the reflection. In reality, the highlight value of most objects is around 0.5, and there are very few non-reflective objects;

• The default value in UE is 0.5.

• The value of 0-1 corresponds to a reflectivity of 0%-8%; 

• Reflectance: When the reflectance is 0%, it is pure diffusion, and the color appears as the intrinsic color; when the reflectance is 50%, the color appears as 50% of the intrinsic color diffusion + 50% reflection; when the reflectance is 100%, the color appears It is a pure reflection, and the color is rendered as a multiplication of the reflected color and the intrinsic color;

• material	specular factor
  Glass	0.5
  plastic	0.5
  skin	0.35
  water	0.255
  ice	0.224

• Specular map:

   

5. Normal

• The height information of the model is recorded by the red and green channels of the map, which is a very economical method for making three-dimensional models;

• Normal map: