When it comes to eye assets, the material carries a lot of the work in the final look of the eye. For that reason, Eye Features Set has pre-made shader node groups that help the user to create the eye material. These node groups use output attributes from the Geometry Node tree and combine them into useful outputs that can be used in the Shader Editor.

In addition to that, there are also pre-made Eye Shader node groups that bundle the entire eye material into a single BSDF-style node with organized controls for the various shading areas of the eye.

Both stylized and realistic eyes use the same shader node groups, which can be imported into the scene through the "Options" menu in the "Shading" section of the add-on:

Helper Shades Node Group

The helper node group, called "Eye Shades" is the basic block for building the eye materials:

"Eye Shades" Settings

Geometry

Outputs from the eye geometry:

Nominal Rec UV - The nominal rectangular UV map. Basic sphere UV, with a seam across the sphere. Useful for radial mapping. Vertical/horizontal texture features get mapped in a radial/concentric manner.
Nominal Polar UV - The nominal polar UV map. Useful for mapping textures to the front of the eye with minimal radial distortion. Textures further back the eye will get more distorted.
Surface Mapping - Uniform mapping of 3D textures on the surface of the eye. Similar to "Object" or "Generated" coordinates, but will deform as the mesh deforms, creating a stable texture under deformation.
Eye Radius - The eye radius value. Useful for scale-dependent settings (e.g. "Height" input of a "Bump" node).

Iris

Outputs for the iris maps:

Iris Gradient - Radial gradient in the iris region
Iris Mask - Adjustable mask for the iris region, including the pupil
IRIS Mask Adjust - Adjust the position of the iris mask border
IRIS Mask Smooth - Smooth the iris mask border

Pupil

Outputs for the pupil maps:

Pupil Gradient - Radial gradient in the pupil region
Pupil Mask - Adjustable mask for the pupil region
PUPIL Mask Adjust - Adjust the position of the pupil mask border
PUPIL Mask Smooth - Smooth the pupil mask border

Sclera

Outputs for the sclera maps:

Sclera Gradient - Main gradient for the sclera, spanning from the back of the eye to the front
Veins Map - Procedural texture for the veins of the sclera

Veins Texture

Settings for the veins texture:

Amount - The number of main vein branches
Levels - Amount of veins per main branch
Seed - Creates different variations of the veins texture

Thickness

Settings for the thickness of the veins:

Thickness - Main thickness of the veins
Thickness Factor - Controls how quickly the veins "thin out" towards the front. Higher values will result in a more drastic transition between thick/thin.
Thickness Randomize - Randomize the thickness of each vein

Reach

Settings for the reach of the veins:

Reach - Controls how far the veins "reach" towards the iris
Reach Randomize - Randomize the reach of each vein
Splits Depth - Controls the depth at which the veins start to split from the main branch. Higher values moves the split-off point deeper, towards the back of the eye.

Distortion

Settings for the distortion of the veins:

Distortion - General factor for the veins distortion noise
Distortion Scale - Scale of the veins distortion noise
Distortion Detail - Amount of detail in the veins distortion noise

Cornea

Outputs for the cornea maps (outer transparent layer):

Cornea Layer Mask - Selection for the outer transparent layer
Cornea Gradient - Main gradient for the cornea, spanning from the back of the eye to the front
Cornea Mask - Adjustable mask for the front of the cornea (cornea bulge) region
CORNEA Mask Adjust - Adjust the position of the cornea mask border
CORNEA Mask Smooth - Smooth the cornea mask border

Eye Shader Node Group

The Eye Shader node group is available in a Stylized and Realistic variant.

The node tree structure inside of the groups is identical for both variants, the difference is in the default values for the settings:

Bellow is a short description for the inputs and outputs of the Eye Shader node group (both variants):

Main Outputs

BSDF - The output surface shading

Thickness - Thickness value, used for the "Thickness" socket of the Material Output node. Used to achieve proper shading of the cornea transparency when using EEVEE.

Sclera

Settings for shading the sclera:

Base Color - The base color for the sclera
SCLERA Roughness - Specifies microfacet roughness of the surface for specular reflection and transmission. A value of 0.0 gives a perfectly sharp reflection, while 1.0 gives a diffuse reflection.
SCLERA Specular - Adjustment to the IOR to increase or decrease intensity of the sclera specular layer. 0.5 means no adjustment, 0 removes all reflections, 1 doubles them at normal incidence.
SCLERA IOR - Index of Refraction (IOR) for specular reflection and transmission. The default value of 1.45 is a good approximation for the eye tissue
SCLERA Subsurface Weight - Blend between diffuse surface and subsurface scattering. Typically should be zero or one (either fully diffuse or subsurface)

Redness

Settings for the sclera redness (Base sclera blood shading, using a noise texture):

Redness Color - Color for the redness
Redness Amount - Grow/shrink the redness gradient
Redness Contrast - Contrast for the redness gradient
Redness Noise - Redness noise factor
Redness Noise Scale - Redness noise scale
Redness Noise Detail - Redness noise finer detail amount

Sclera Redness view:

Veins

Settings for the sclera veins texture:

Veins Color - Veins color
Veins Strength - Veins texture strength amount
Veins Amount - Number of main veins. Each main vein can have split-off veins.
Veins Levels - Number of secondary split-off veins
Veins Seed - Variations of the veins texture

Thickness

Settings for the veins thickness:

Thickness - Main thickness for the veins
Thickness Factor - Controls how far the main thickness reaches the end of the veins, before they start to thin out
Thickness Randomize - Varies the thickness of each vein

Reach

Settings for the veins reach (How far the veins extend towards the iris):

Reach - How far the veins extend towards the iris
Reach Randomize - Varies the reach of each vein
Reach Splits Depth - Controls when the split-off veins start to separate from the main vein

Distortion

Settings for the veins distortion/waviness:

Distortion - Amount of distortion/waviness of the veins
Distortion Scale - The scale of the distortion noise
Distortion Detail - Veins distortion noise finer detail amount

Sclera Veins view (exaggerated for visibility):

Iris

Settings for shading the iris:

IRIS Roughness - Specifies microfacet roughness of the surface for specular reflection and transmission. A value of 0.0 gives a perfectly sharp reflection, while 1.0 gives a diffuse reflection.
IRIS Specular - Adjustment to the IOR to increase or decrease intensity of the iris specular layer. 0.5 means no adjustment, 0 removes all reflections, 1 doubles them at normal incidence.
IRIS Boundary Smooth - Smooth the boundary of the iris region to blend between the iris/sclera
IRIS Boundary Adjust - Adjust the iris boundary position

Iris Colors

Inner/outer color gradient for the iris:

Outer Color - Outer color for the ciliary region of the eye (near the iris border)
Inner Color - Inner color for the ciliary region of the eye
Colors Mix Adjust - Adjust the position of the color gradient midpoint
Colors Mix Contrast - Contrast the iris color gradient

Iris Colors gradient:

Rim Shadow

Settings for the iris rim shadow. Used to darken the iris perimeter:

Rim Shadow Strength - Strength of the shadow darken
Rim Shadow Grow - How far the shadow reaches towards the pupil
Rim Shadow Contrast - Contrast of the shadow gradient

Iris boundary (Rim) shadow:

Iris Shadow/Highlight

Settings for the iris shadow/highlight spot. Used to create a depth effect, caused by light coming from above and casting a shadow from the top eye lid:

Iris Shadow/Highlight Strength - Strength for the shadow/highlight darken/lighten effect
Shadow Value - Strength of the shadow darken
Highlight Value - Strength of the highlight lighten
Iris Shadow/Highlight Shift - Shift the shadow/highlight spot away from the pupil
Iris Shadow/Highlight Shift Angle - Angle to rotate the shadow/highlight spot by around the pupil
Iris Shadow/Highlight Spot Size - The size of the shadow/highlight spot
Iris Shadow/Highlight Spot Contrast - Contrast of the shadow/highlight spot

Iris Shadow/Highlight view:

Pupillary Zone

Settings for the pupillary zone (Inner iris spot):

Enable Pupillary Zone - Enable to add a the pupillary zone features of the iris
Pupillary Color - Color for the pupillary region of the eye (Inner region)
Pupillary Zone Seed - Variation in the shape of the pupillary zone spot
Pupillary Zone Size - The size of the pupillary zone spot
Pupillary Zone Scale - Scale for the distorting noise of the pupillary zone spot
Pupillary Zone Detail - Fine detail for the distorting noise of the pupillary zone spot

Collarette Highlight

Settings for the collarette (pupillary zone border) highlight:

Collarette Highlight Strength - Amount of collarette highlight lighten
Collarette Highlight Contrast - Contrast for the collarette highlight region
Collarette Highlight Adjust - Adjust the thickness of the collarette highlight region

Iris Pupillary Zone view:

Iris Fibers

Settings for the iris fibers (Radial bands):

Iris Fibers Strength - Strength of the iris fibers effect
Iris Fibers Seed - Variations for the iris fibers texture
Iris Fibers Ciliary Scale - Scale for the iris fibers noise in the ciliary zone
Iris Fibers Pupillary Scale - Scale for the iris fibers noise in the pupillary zone
Iris Fibers Ciliary Contrast - Contrast for the iris fibers noise in the ciliary zone
Iris Fibers Pupillary Contrast - Contrast for the iris fibers noise in the pupillary zone
Iris Fibers Distortion - Distortion of the iris fibers noise
Iris Fibers Distortion Scale - Scale of the of the iris fibers noise distortion

Iris Fibers view:

Ciliary Rings

Settings for the concentric iris rings, found in the ciliary zone:

Ciliary Rings Strength - Strength of the ciliary rings effect
Ciliary Rings Amount - Number of ciliary rings
Ciliary Rings Blur - Smooth the ciliary rings texture
Ciliary Rings Distortion - Distortion of the ciliary rings texture. Used to create waviness in the rings.
Ciliary Rings Distortion Scale - Scale of the of the ciliary rings noise distortion

Iris Ciliary Rings view:

Radial Highlights

Settings for radial streaks of highlight in the iris:

Radial Highlights Strength - Strength of the Radial Highlights effect
Radial Highlights Color - Color of the highlights
Radial Highlights Angle - Angle of the highlights mask
Radial Highlights Mask Size - The size of the highlights mask
Radial Highlights Mask Contrast - Contrast for the highlights mask
Radial Highlights Position - Position of the highlights along the iris width
Radial Highlights Length - Length of the highlights streaks
Radial Highlights Contrast - Contrast for the highlights streaks
Radial Highlights Scale - Scale of the highlights streaks
Radial Highlights Detail - Amount of detail in the highlights streaks

Iris Radial Highlights view:

Freckles

Settings for the iris freckles (spots):

Freckles Strength - Strength of the spots effect
Freckles Color - Color of the spots
Freckles Size - The size of individual spots
Freckles Contrast - Contrast for the spots
Freckles Scale - The amount of spots
Freckles Seed - Seed for the spots position
Freckles Distortion - Distortion for the spots shape
Freckles Distortion Seed - Seed for the spots distortion
Freckles Mask Size - Size of the freckles mask
Freckles Mask Contrast - Contrast for the freckles mask
Freckles Mask Angle - Angle for the freckles mask

Iris Freckles view:

Iris Bump

Settings for the iris bump. Positive values raises the surface, negative ones push inwards:

Bump Strength - Overall factor for the bump strength values
Iris Fibers Value - Strength of the iris fibers bump
Pupillary Zone Value - Strength of the pupillary zone bump
Pupil Dip Value - Strength of the bump, used to simulate a dip in the iris surface around the pupil
Freckles Value - Strength of the freckles bump

Iris Bump view (cornea layer hidden for clarity):

Pupil

Settings for shading the pupil:

Pupil Color - Color for the pupil. In most cases, the pupil color should be pure black, to simulate the pupil hole.
Pupil Specular - Specular IOR for the pupil. In most cases, the pupil specular should be 0.0, since there is no surface at the pupil hole.
Pupil Boundary Smooth - Smooth the boundary of the pupil region to blend between the iris/pupil
Pupil Boundary Adjust - Adjust the pupil boundary position

Example of using unnatural pupil shape and color to achieve a stylized look:

Cornea

Settings for shading the cornea (Use these settings in the material for the transparent outer layer):

CORNEA Roughness - Specifies microfacet roughness of the surface for specular reflection and transmission. A value of 0.0 gives a perfectly sharp reflection, while 1.0 gives a diffuse reflection.
Cornea IOR - Index of Refraction (IOR) for specular reflection and transmission. The default value of 1.38 is a good approximation for the transparent cornea layer of the eye.

Color Tint

Settings for the outer layer tint:

Tint Color - Color for the cornea tint. Use colors with a value of 1.0 to preserve pure cornea transparency.
Tint Factor - Strength of the color tint

Cornea Tint view:

Fake Highlight

Adds up to two fake highlight spots on top of the cornea:

Spot 1

Settings for the first highlight spot:

Spot 1 Spot Strength - The strength of the first highlight spot effect
Spot 1 Spot Mapping - How the first highlight spot is mapped to the front of the eye, using either the rectangular or polar UV map of the cornea
Spot 1 Spot Shading - Shading method for the first highlight spot - Color or Shader
Spot 1 Spot Color - The color of the first highlight spot
Spot 1 Spot Shader - Custom shader for the first highlight spot

Spot 1 Shape

Settings for the shape of the first highlight spot:

Spot 1 Shape Spot Type - The shape of the first highlight spot
Spot 1 Shape Spot Width - Width of the first highlight spot
Spot 1 Shape Spot Height - Height of the first highlight spot
Spot 1 Shape Spot Shape - Adjust the shape of the first highlight spot
Spot 1 Shape Window Bars - Adjust the width of the window bars of the first highlight spot

Spot 1 Transform

Settings for moving and blurring the first highlight spot:

Spot 1 Transform Offset Spot - Move the first highlight spot away from the cornea center
Spot 1 Transform Revolve Spot - Revolve the first highlight spot around the cornea center
Spot 1 Transform Rotate Spot - Rotate the first highlight spot
Spot 1 Transform Keep Rotation - Keeps the orientation of the first highlight spot when revolving around the cornea center
Spot 1 Transform Blur Spot - Blur the first highlight spot

Spot 2

Settings for the second highlight spot:

Spot 2 Spot Strength - The strength of the second highlight spot effect
Spot 2 Spot Mapping - How the second highlight spot is mapped to the front of the eye, using either the rectangular or polar UV map of the cornea
Spot 2 Spot Shading - Shading method for the second highlight spot - Color or Shader
Spot 2 Spot Color - The color of the second highlight spot
Spot 2 Spot Shader - Custom shader for the second highlight spot

Spot 2 Shape

Settings for the shape of the second highlight spot:

Spot 2 Shape Spot Type - The shape of the second highlight spot
Spot 2 Shape Spot Width - Width of the second highlight spot
Spot 2 Shape Spot Height - Height of the second highlight spot
Spot 2 Shape Spot Shape - Adjust the shape of the second highlight spot
Spot 2 Shape Window Bars - Adjust the width of the window bars of the second highlight spot

Spot 2 Transform

Settings for moving and blurring the second highlight spot:

Spot 2 Transform Offset Spot - Move the second highlight spot away from the cornea center
Spot 2 Transform Revolve Spot - Revolve the second highlight spot around the cornea center
Spot 2 Transform Rotate Spot - Rotate the second highlight spot
Spot 2 Transform Keep Rotation - Keeps the orientation of the second highlight spot when revolving around the cornea center
Spot 2 Transform Blur Spot - Blur the second highlight spot

Cornea Fake Highlight examples (Superellipse and Window shapes):

Setting up the Materials

The eye assets use two materials to achieve the final shading of the eye - the eye and cornea material.
The cornea material is usually a transparent glossy material, so to achieve proper shading in EEVEE, a few considerations have to be taken into account:

1. In the EEVEE render settings, "Raytracing" needs to be turned ON:

2. In the Eye material settings, "Render Method" needs to be set to "Dithered" and "Raytraced Transmission" needs to be OFF.

3. In the Cornea (transparent) material settings, "Render Method" needs to be set to "Dithered" and "Raytraced Transmission" needs to be ON: 

Additionally, the Thickness output of the cornea (transparent) material has to have a value of 0.0 plugged in (or some other very small value). If the "EFS Eye Shader" node is used, it has a Thickness output for convenience, so that can be used instead: 

or

Automatic Material Setup

Eye Features Set offers an function to set up the previous steps automatically, as well as importing and applying the materials shader setups from the add-on installation files. Materials can be set up for either stylized or realistic styles, independent from the asset style type: