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Excellent overview of unreal Ray-Tracing stuff, thank you! Any chance you can add the scene to the asset pack?
So what's exactly the advantage? good would be a direct comparison to known renderers
Have a look at a thorough tutorial on creating eyes with ZBrush by Jason Hill. The guide is suitable for beginners and for anyone having a hard time dealing with intricate details. Basically, this is perfect beginner’s guide that will lead to generating an asset ready to be used in all kinds of projects.
The first part of any project is to collect good reference for what you’re gonna work on. Get a range of detailed images to give yourself some options and different perspectives. Try and cover your bases so think of as many aspects you’re unclear on as possible. Here’s the Pinterest board of reference I used
MODELS & SCULPTING
We will be making two Models. the Inner Eye model with the iris and pupil and the Outer Eye model with the cornea. Here’s a look at the final models
So first things first. We start with a sphere, which isn’t as straight as it could be. In the tools pane select a sphere and make it a polymesh so we can work with it. After making it a polymesh we are going to rotate it 90 degrees to get the topology flowing forwards which we will use to make the pupil hole and give us a nice edge flow for the shapes we will be making. Before we do anything else, duplicate this so we have the two identical starting spheres to work with. You can Hide one of them so we can focus on one at a time.
With our first sphere we will make the Inner eye model. That will consist of making the pupil hole, defining the iris shape, and giving the model thickness.
First hide the polygons you want to delete to make the pupil hole. You can hide/unhide until you get the size you want. Next you can use the ClipCurve brush to clip the eye from the side to flatten out the iris quickly. Next we will use some tricky shit to give it thickness. This method will work without Zmodeler. First invert the mesh so its inside out, then you’ll use panel loops to extrude it and bevel the edge (check settings below) By inverting it first it extrude inward instead of outward, giving us depth and keeping the size and shape we had. Now lets make a polygroup for the whole eye then one just of the Iris to make our selecting easier. Then by Ctrl+Shift Clicking the Iris we hide the rest. Ctrl Clicking the Canvas masks all visible. Unhide the rest and Ctrl click the ball, blurring your selection so we can get a nice soft concaved Iris (press W and position action line from the side and translate it inward)
Now we can divide up to get more resolution to sculpt the details of the Iris. We’ll create some fibers first which we can blur and add more and more on top giving a layered effect of fibers flowing inward. Activate Radial Symmetry from the Transform Menu. Set your brush up with spray and the lines alpha. now spray some lines flowing inward. Try doing it large then smoothing it a bit and adding more, mess around and see what looks good to you. Then to get the more complicated fibers and folds along the center we can draw out our shape as a mask to inflate and push up. Take your time to mask out a shape you like based on your reference. Keep the brush small to get get a crisp edge toward the center and you can lightly feather and blend out the outer edge with a larger brush size.
Back to the second sphere to make the outer Eye model, or “Cornea.” Now we can quickly make the outer Eye model by inflating the sphere a little, in this case by “5” to get it like an outer shell to the inner Eye model. Then by making a blurred mask the size of our Iris (use transparent view to see both models) we can extend the the cornea out as a smooth convexed dome.
Painting and textures
I painted the colors and patterns in Zbrush using polypaint and did some balancing with Photoshop as well as create a mask to make Color Variations. PSD is included in the download. I use Photoshop CC at home because its always up to date and relatively inexpensive. I got the Photography bundle and pay 10$ a month which is worth it to me since I use Photoshop A LOT. Here is an affiliate link for Photoshop CC if you want to check it out for yourself.
Onto the Iris painting, first we lay down a dark blue then lightly we add a lighter blue to the center to get a gradient. Then the same way we sculpted the fibers we are going to add fibrous color variation. Then we can paint some highlights by hand, choose another light blue and start brushing the the edges of things and you can add some lines fading out from the center. We can then pop out some of our detail we sculpted by masking by cavity then lightly brushing a highlighting color over the middle, try inverting the mask or blurring it and painting darker colors. Lastly fix up anything by painting by hand and to finish it up add some brown spots here and there to add some contrast and character.
After the Iris is done the last thing to paint is the blood and veins. This is a pretty quick method to just get some random lines and detail in there. This is a small detail in most characters so don’t get caught up on parts you can’t see or barley see. First we spray a bloody red color all over and fade it up to the Iris. Then drag out some vein stamps to quickly add detail and fill it out. Lastly paint some hero veins by hand. To get a smoother clean line turn on Lazymouse.
Now lets turn our Polypaint into an Image file to use as a texture so we can edit it in Photoshop and apply it in our render program. First we need to create UVs for our model to transfer the color info to. Open UV Master from the plugins menu and with Symmetry on hit Unwrap. Then in the Texture Map pane click “New from Polypaint” under Create. Then to get it over to the texture pan click “Clone Txtr” at the top. Then from the Textures menu we can export.
I use Keyshot and the Keyshot Bridge to render my eye which makes it super easy but these files can be used in any Raytrace Renderer. To render our eye in any another program we need to export the two models and texture and import them, Keyshot Bridge does this automatically.
Once in Keyshot all we do is choose our environment and drop some materials onto the two models to start with.
The two materials we will start with are Plastic for the inner Eye and Glass for the outer Eye. Apply the Plastic material to the inner Eye and choose the Texture we made for the Diffuse. *In Keyshot Bridge you then need to select UV Coordinates as the Type and 0 out the settings below. The inner Eye doesn’t need to be shiny, my specular is all the way down, the reflection comes from the Outer Eye.
The outer eye model plays two important roles in the appearance of the Eye. It is what is most reflective and wet looking as well as refractive. Refraction is what happens when light moves through transparent things and why things in glass or water appear different. Its also an aspect of the human eye and gives the iris a distinct look from all angles. The “index of Refraction” of glass is around 1.5, it varies from material to material but its what Keyshot’s glass shader defaults to. By googling “refraction index of Cornea” we find that the Human Cornea has an index of about 1.376 which visually makes little difference but makes it so much more fuckin cool.
That’s it! You should now have an Eye model of your own. Remember you can make a variety of eye shapes and colors by modifying this model and method. So save your Eyes to stick in a monster head or something. These are the models I used for Hanza.