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Eyes modeling can be very simple if you follow some easy steps. First, create a sphere with 20 segments (Fig.01a). Duplicate the sphere and rename one of them "IN" and the other "OUT" so they will be easier to recognize. Put the spheres in a group and call it "Group_Eye". Now set the group as a HyperNURBS Object (Fig.01b). Select the sphere called "IN" and scale it slightly inwards. You can also give a Scale value in the window coordinates (Fig.01c). Select the sphere again, shift it along the X axis and place it next to the sphere called "OUT" (Fig.01d).
Select the Knife tool in Loop mode and un-check Restrict to Selection. Select the IN sphere and the cuts will affect the last row of the sphere's polygons, thus creating the iris. The first cut creates the pupil size, the second cut should be close to the first cut, the third midway between the pupil and the iris's end, and the last near the inner edge of the iris. The same operation should then be carried on the OUT sphere, with the exception of the second cut near the pupil (Fig.02a).
Select the points created by the new cuts on the OUT sphere, push them out and give it a dome shape (Fig.02b). At the end of the dome select alternate parts of the central ring and delete them (right-click > Dissolve) (Fig.02c).
Select points previously created and push them to create a concave shape (Fig.03a). Select the sphere's center point and delete it with the Delete key. Select the ring of the pupil's point and push it slightly inward (Fig.03b). Bring the sphere to 0 on the coordinates so that the two spheres overlap again (Fig.03c). Choose the OUT sphere, give it a new material and rename it "Eye Out". Open the Material Editor and activate the Transparency with a Brightness of 90%, and a Specular Refraction of 1.1. Now activate the Specular and set it to Width: 20, Height: 200, Fall Off: 20 and Inner Width: 20 (Fig.03d).
Create a new Sphere (Fig.04a) and delete 80% of it (Fig.04b) to produce a small disk that you should call "PUPIL" (Fig.04c). Create a new material and name it "pupil". Open the Material Editor and un-check all the items until you get a completely black material. Now you want to attribute the new material to the object you just created (Fig.04d).
Enter the new PUPIL object in to the Group Eye and place it inside the IN sphere near the iris so the light does not penetrate into the eye (Fig.05a). Now switch to BP UV Edit mode. Switch on the front view and in the UV mapping section give a front projection to the IN sphere (Fig.05b). Select the UV of the latter half of the sphere, scale it in the UV editor and place it in the UV space corners (Fig 05c). This way we give all the importance to the front part of the eye. Create a new material and call it "iris". Double click the material in the Material Editor, click on the texture and select Create New Texture. A new window will be opened into which you can insert the name of the map (in this case "Iris_Color") and choose the map size, 1024 x 1024 (Fig.05d).
At this stage I will show you how to create an iris, although there is also the option to use the image of an iris from a photo. In both cases, the next steps will show you how to use the maps in the various channels. First, select the Hyper NURBS object, switch in the Catmul Clark and, in the Attributes option, change the Subdivide UVs in EDGE so the smoothed UV follows the same mesh course. Now make this visible in the UV selected and in the UV Mesh select Show UV Mesh. As the last step, before you start go to Object Panel > Layer Manager and select Edit (expanded/compact). This way the management level will be very similar to other programs (Fig.06a). Attribute the IN sphere with the Iris_Color material. Choose a yellowish white and fill the Layer tool in white across the sphere (Fig.06b). Create a new layer and call it "Iris" (Window Materials > Texture > New Layer). Create a circular selection that delimits the iris. Under the Window tab, select Choose Feather and set the value to 5. Choose the color you want the eye to be, and fill the colored section (Fig.06c).
Create a new layer and rename it "Iris Light". Select the Dodge tool and set it as Mid-tones. Vary the pressure and the hardness in order to obtain the soft light on the inner edge of the iris (Fig.07a). Now select the Smear tool and set the brush size to a low value. Again with the active selection use the Smear tool on the iris ? it gives a less precise and more natural appearance to the eye (Fig.07b).
Once the iris is complete duplicate the layer (right-click on the current level), select the Burn tool and set it to Mid-tones. Adjust the size, pressure, and hardness in such a way as to obtain a fairly soft brush. Now you are going to darken the inner profile and center of the iris (Fig.08a). If the iris looks too dark or light, select the filter level located below the window Filter > Color Correction and calibrate the intensity of the map to your liking (Fig.08b). Create two new layers that you will rename "Red" and "Veins". Select the Red layer and, with the soft brush, paint the outside of the eye. Then select the Veins layer and, with a small brush, draw the veins on the eye to make them look more realistic (Fig.08c).
Open the Material Editor and select and activate Bump. Create a new texture that we will call "Eye_Bump" (Fig.09a). Select the Veins layer previously created in color map and select the entire workspace (Ctrl + A). Copy the veins texture (Ctrl + C) then select the bump layer and paste the veins texture. This will create a new layer containing the veins textures in grayscale and in the same position as the veins that are in color (Fig.9b). Open the Material Editor again and select and activate Specular Color. Create a new texture that we can call "Eye_SpecularColor" (Fig.09c). Copy the color from the iris texture and paste it in the Specular map, repeating the same operations as you did earlier for the veins texture. Here you will create a new layer with a grayscale iris. (Remember that the Specular map can be colored. For example, if you put a blue color into the Specular map the result we will get from the light source will be shades of blue instead of white)(Fig.09d).
Select the Specular map texture and, using levels, correct it to give it more light colors and sharpen the map (Fig.10a). In the Material Editor select Specular and attribute it to the material; the result will be that of a smooth specular (Fig.10b). Now select the OUT part, open the Material Editor and activate Voice Material Reflection (Fig.10c). If your scene does not include an environment from which the reflection takes information you can attach a map like a HDRI to make it look more realistic.