HumanSkin Shader

Overview

The HumanSkin shader is a specialized shader for rendering skin surfaces as skin shading cannot be accurately reproduced using regular lighting models.

Shader Params

Shader Params	Description	Shader gen option
Detail bump scale	Controls the strength of the detail normal map Default value: 0.5	Detail normal map
Displacement bias	See Displacement/Phong/PN Triangles Tesselation - Shader Generation Params for more information. This parameter requires that Displacement mapping is enabled in the Shader Generation Parameters.	Displacement Mapping
Displacement height scale	See Displacement/Phong/PN Triangles Tesselation - Shader Generation Params for more information. This parameter requires that Displacement Mapping is enabled in the Shader Generation Parameters.	Displacement Mapping
Indirect bounce color	Sets the amount of indirectly bounced color.	All
Melanin	Legacy feature. Controls the amount of pigmentation in the skin Default value: 0.0	All
SSS Index	Functionally obsolete. The skin shader is locked to the skin SSS range (1.001 to 1.999) by default.	All
Tessellation face cull	See Displacement/Phong/PN Triangles Tesselation - Shader Generation Params for more information. This parameter requires that Displacement Mapping is enabled in the Shader Generation Parameters.	Displacement Mapping
Tessellation factor	See Displacement/Phong/PN Triangles Tesselation - Shader Generation Params for more information. This parameter requires that Displacement Mapping is enabled in the Shader Generation Parameters. Default value: 1	Displacement Mapping
Tessellation factor max	See Displacement/Phong/PN Triangles Tesselation - Shader Generation Params for more information. This parameter requires that Displacement Mapping is enabled in the Shader Generation Parameters. Default value: 32	Displacement Mapping
Tessellation factor min	See Displacement/Phong/PN Triangles Tesselation - Shader Generation Params for more information. This parameter requires that Displacement Mapping is enabled in the Shader Generation Parameters. Default value: 1	Displacement Mapping
Translucency Multiplier	Controls strength of the SSS feature. Defaultvalue: 0.7	All
Wrinkles blend	Controls strength of the wrinkle map. Default value: 1	Wrinkle blending

Shader Generation Params

Parameters	Description
Wrinkle Blending	Enables the use of sub surface map Alpha for wrinkle blending.
Decal Map	Enables the use of a decal map, which is blended on top of the diffuse map.
Detail Normal Map	Enables the use of a tiled detailed map for pores and tiny details (_ddn).
Subsurface Scattering Mask	Enables the use of diffuse map alpha as an SSS amount multiplier.
Displacement Mapping	Enables the use of displacement mapping, which requires a height map (_displ).
Phong Tessellation	Enables the use of a rough approximation of smooth surface subdivision.
PN Triangles Tessellation	Enables the use of a rough approximation of smooth surface subdivision.

Using the HumanSkin Shader

The HumanSkin shader is fully integrated with the Physically Based Shading model. Most tweaking takes place directly via the individual texture maps, with individual attributes of the shader being locked to the physically correct values. This enhances usability and ensures consistency between assets. HumanSkin features some unique texture slots to give artists control over the specific features of the shader.

Diffuse

It's generally advisable to author 'flat' diffuse maps. I.e. when basing textures off photographs or scan information, it's key to remove most lighting information. When hand-painting diffuse maps, the focus should be on color and hue changes. An exception to this is high-frequency Ambient Occlusion/Cavity information, which can be added to fake detail occlusion and shading.

Specular Map

In order to achieve a physically correct representation of human skin in the PBR model, a flat base-value of 51 should be used for the specular map. Adding subtle pore detail on top of that (simulating high frequency occlusion) will generally give the most convincing results. Also, to compensate for precision issues with occlusion and shadow casting, it can be helpful to paint in/darken details such as nostrils, cavities of the ear, etc.

Bump Map (Normal Map)

For best results, it is advisable to experiment with the strength of high-frequency details on the high-poly source asset – i.e. keeping such details on a separate layer(s) in the digital sculpting app, can be helpful.

Gloss (Normal Map Alpha)

On the large scale, the gloss map should capture how oily/shiny certain areas of e.g. a face. This adding high contrast details will help to break up specular highlights and improve the look.

Detail

The selected map will be overlayed with the base Normal Map – an easy way to add very high-frequency detail to a model and further break up specular highlights. Tiling can be controlled in the tiling subsection of the texture slot.

Detail Normal Map must be turned on in the Shader Generation Params.

Opacity Map (SubSurfaceScattering)

The SSS map should represent thin areas of skin that can readily be penetrated by light (e.g. ears, nostrils, etc.). SSS maps can be either manually authored or baked with an appropriate tool.

Decal

Will overlay a secondary diffuse map (requires an alpha channel). This is useful to create variation of existing textures, e.g. add tattoos, warpaint or dirt.