misss_fast_skin

Category: mental ray > Material Phenomena

Shader Family: Material Phenomenon

Output: Custom

This is an advanced phenomenon for skin shading that includes three-layer scattering and skin-specific specularity options. Skin is simulated in layers as follows:

A top reflective sheen layer (for specularity and surface non-scattered Lambertian diffuse reflections).
A dual-layer subsurface scattering (simulating both the scattering in the epidermis and the layers below, collectively named "subdermal").
A "through" scattering from the back.

The parameters lightmap, depthmap, lightmap_group, lightmap_size, samples, bump, ambient, lightmap_gamma, indirect, scale_conversion, scatter_bias, falloff, and screen_composit all work identically to their counterparts in misss_fast_simple_phen (refer to this shader for all of these parameter descriptions).

All other parameters are handled somewhat differently for the misss_fast_skin_phen and are discussed further in the table below.

Name	The name of the shader node displayed in the render tree. Enter any name you like, or leave the default.
overall_color	The overall coloration of all diffuse components. This color will affect all the underlying layers (unscattered, epidermal, subdermal, and back) and is good for overall color tweaks, or texture mapping surface features that should block out underlying light, such as skin moles, textured eyebrows, dirt, etc.
diffuse_color diffuse_weight	The color and weight of the normal Lambertian diffuse component. This represents the very top layer of the skin where all the tiny bumps are located. For caucasian skin the color would be mostly white with perhaps a small amount of blue and an appropriate diffuse weight would be around 0.3.
front_sss_color front_sss_weight front_sss_radius	The color, weight, and scatter radius within the epidermal skin layer, which is the whiteish/yellowish layer just under the surface. Good values are a slightly yellowish color, a weight of 0.5, and a radius of around 5 to 10mm (0.2 to 0.4 inches).
mid_sss_color mid_sss_weight mid_sss_radius	The color, weight, and scatter radius of the underlying subdermal skin layer. They function the same as the front_sss parameters, but for the layer below the top layers, representing the deeper, reddish, 'meaty' scattering. A reddish/orangeish color with a weight of around 0.5 and a radius of 10 to 25mm (0.4 to 1.0 inches) is a good starting point for experimentation.
back_sss_color back_sss_weight back_sss_radius back_sss_depth	These options represent light going straight through the flesh, for example, to achieve the "red ears" look.
overall_weight	The overall level of specularity and reflections. Generally, any specularity map can be used and will affect the level of all the specularity options that follow below.
edge_factor	Sets the "edge width" of the edge reflection effects. Skin reflects more when looked at from angles nearly perpendicular to it (known as the "Fresnel effect") and this parameter sets the narrowness of this edge. Higher values yield a thinner edge. The edge width applies to all the edge weights listed below.
primary_spec_color primary_spec_weight	The color and base weight of the first layer of specularity. Skin specularity has two-layers allowing the simulation of both the broad soft specularity of skin and any near-reflective specularities of top layer oiliness and wetness.
primary_edge_weight	Sets an additional multiplier for the edge, where final specularity at the edge is the sum of weight and edge weight.
primary_shinyness	The specular exponent. Higher values yield a smaller and sharper specular highlight, which is a modified Phong model with edge softening.
secondary_spec_color secondary_spec_weight secondary_edge_weight secondary_shinyness	Function the same as the primary_ parameters, but are used for the second layer of specularity. For skin, a good rule of thumb is to have a 1st specular layer with a very low shinyness (3.0 to 8.0) and a low level (0.1 to 0.3) but a rather high edge weight (0.5 to 1.0) and a slightly blueish color, and a 2nd layer that has high shinyness (20 to 100) and a medium level (0.3 to 0.6) and no edge enhancement. Introducing mapping into the specularity channels enhances realism greatly.
reflect_weight reflect_edge_weight	The weight and edge weight for reflections. When set to a non-zero value, actual glossy reflections are added.
reflect_shinyness	The shinyness value for glossy reflections. When set to 0 (zero), standard raytraced mirror reflections are used, but for non-zero values glossy reflections are generated, which increases render time.
reflect_environment_only	When on, only the current environment map is sampled for reflections, and no actual rays are traced.
environment	Pick a local environment shader.