PBR parameters

PBR Lighting Model Components

Name	Description	Components
Indirect Diffuse	Models diffuse lighting from the environment.	Specified by a special diffuse texture created from the sky texture. Controlled via envmap_intensity in the environment. Affected by the angle of incidence.
Indirect Reflection	Models environmental reflections.	Specified by a special specular texture created from the sky texture. Controlled via envmap_intensity in the environment. Affected by the angle of incidence and surface roughness.
Direct Diffuse	Models lighting by a light source on matte surfaces.	Set in the environment as diffuse*diffuse_intensity Affected by the angle of incidence.
Direct Reflected	Models lighting by a light source on glossy surfaces.	Set in the environment as diffuse*diffuse_intensity Affected by the angle of incidence and surface roughness.

Key PBR parameters

Diffuse

(Also known as Albedo) Reflects the color of the material without considering lighting. This texture defines the basic color of an object under white light, making it a fundamental texture for most materials in 3D scenes.

Texture name	Components	Map decryption
<name>	3 channels in sRGB gamma space	The map contains the color information of each surface pixel under white light

Diffuse maps do not contain information about the glossiness or reflectivity of the material; these aspects are controlled by other texture maps.

Diffuse values can't be near zero since even materials like soot and coal reflect some light.

Ambient Occlusion

Essential for ensuring that indirect lighting does not illuminate gaps in objects such as tree trunks, dark spaces between pipes, and similar areas. This texture setup helps to realistically portray how light interacts with complex surfaces by emphasizing areas that should remain dark due to blocked light sources.

Texture name	Components	Map decryption
<name>_ao	1 channel linear space ranging from [0..1]	White areas in the texture represent open parts of the model. Black areas are fully self-shadowed regions where diffuse light cannot reach. Dark areas define parts of the model or material that are shadowed from external lighting due to obstructions by other parts of the model or material.

Metallic

Metallic texture is crucial for simulating metallic materials in models, as metallic components reflect light differently compared to dielectrics.

Texture name	Components	Map decryption
<name>_mt	1 channel linear space ranging from [0..1]	Black represents non-metallic parts of the model (dielectrics). White indicates metallic areas. Intermediate values are used for regions where metal partially appears.

The diffuse color defines the inherent color of the metal where metallic is non-zero.

The metallic should be set to 0 for non-metallic materials such as soil, water, stones, tree bark, leaves, wood, and concrete.

Roughness

Roughness texture determines the light reflection pattern on a surface based on the physical properties of the material, thus affecting the perception of the material's realism.

Texture name	Components	Map decryption
<name>_rg	1 channel Linear space ranging from [0..1]	Black represents smooth surfaces such as glass or calm water. White indicates rough surfaces like dry dirt or dust. Intermediate values determine the degree of roughness.

Roughness values close to 0 should be avoided as they produce very small, high-contrast highlights, leading to aliasing in the image.

Normal

The Normal map texture simulates detailed surface relief by reflecting light, applicable in both PBR and Phong lighting models.

Texture name	Components	Map decryption
<name>_nm	3 channels in sRGB gamma space	Each pixel contains normal coordinates encoded in RGB channels as XYZ coordinates.

The difference between normal maps for OpenGL and Direct3D (DirectX) lies in the orientation of the green channel (Y-axis). In OpenGL, the green channel is positive (Y+), indicating that normals are lit from above. In contrast, Direct3D (DirectX) uses a negative green channel (Y-), which suggests that normals are lit from below. This difference affects how light and shadow are perceived on textured surfaces within 3D environments.

Lightmap

Lightmap contains pre-calculated diffuse lighting information for use in scenes, useful when local ambient occlusion for the material and a global map for the entire object are present.

Texture name	Components	Map Decryption
<name>_nlm	1 channel in linear space ranging from [0..1]	Black areas denotes fully shaded areas of the model. White areas indicates illuminated areas. Intermediate values represent varying degrees of lighting.

Usage examples:

• A fence model utilizes a tiled material texture with an ambient occlusion map and a lightmap for the assembled fence.

• A tank's tracks model includes an ambient occlusion texture for a tiled section of the track and a lightmap accounting for both the tank and the position of the rollers.

Translucency

Translucency map texture dictates the translucency and thickness of the material, determining how much light passes through.

Texture name	Components	Map decryption
<name>_tl	1 channel Linear space [0..1]	Black areas represent opaque sections of the model. White areas indicate full transparency. Intermediate values denote varying degrees of translucency.

Usage examples: The channel dictates only light passage; color is determined by the diffuse texture. Used in textures like grass and leaves to prevent them from appearing dark on the side opposite the light source.

Height

Special texture used to simulate three-dimensional details on flat surfaces using parallax technique, enhancing detailed surfaces without significant performance costs.

Texture name	Components	Map decryption
<name>_hm	1 channel Linear space [0..1]	White areas represent "high" points of the surface. Black areas are "low" points. Gray scale indicates various height levels.

Not considered in the current PBR implementation.

Emissive

Texture simulates glowing effects and other light sources that should appear self-illuminating.

Texture name	Components	Map decryption
<name>_em	3 channels Linear space	The color on the map directly influences the color of the emitted light. The intensity of the glow is determined by the color brightness on the map. Brighter colors lead to more intense glow.

Usage example: Ideal for visual representation of light sources within textured objects, often used to add visual depth and enhance scene perception.

Reflectance

Sets the reflectivity for dielectrics, used as a material parameter. The reflectance is fixed at 4% as this is the typical value for most materials.

Texture names in the game resources

Textures from GEM2

File name	Corresponding texture map
<name>	Diffuse
<name>_nm	Normal Map
<name>_sp	Specular
<name>_lm	Light Map
<name>_hm	Height Map
<name>_prlx	Alternative Version of Height Map

Added in PBR

File name	Corresponding texture map
<name>_ao	Ambient Occlusion
<name>_mt	Metallic
<name>_rg	Roughness
<name>_tl	Translucency