Creating eyes in Gimp

A few days ago, I posted an eye I made using Gimp on my Facebook page and promised a tutorial about it. Well, here it is! You may wonder why I use Gimp and not Photoshop or Illustrator? It's very simple: Gimp is free and cross-platform (my PC runs Ubuntu). 

The basics
I started with the basic shape: the background, outline and a pupil. The image is a square image sized 1000 x 1000 pixels, with the grid spacing set to 50 pixels, and will contain a lot of layers. Four layers to get started, named "White background", "Eye background", "Outline" and "Pupil".

The layer "White background" is filled entirely in white, and in the layer "Eye background", a circle filled with solid dark red (RGB color #c80000) measuring 900 x 900 pixels is drawn, using the select and fill tool.
In the layer "Outline", the black outline is drawn. The best way to do this and get a nice, smooth circle is this:

• Select the background circle (in the Layers-tab, right click on the "Eye background" layer and select "Alpha to selection");
• Select the "Outline" layer;
• Select the Paintbrush tool, select the fuzzy round brush with a hardness of 75, and set the size to 5;
• Go to Edit -> Stroke selection -> Stroke with a paint tool and select the Paintbrush tool; make sure "Emulate brush dynamics" is unchecked.

If you use "Stroke line" instead of the Paintbrush tool, the line is much more jagged, even with anti aliasing.

For the pupil, draw an almond shape using the Path tool. In the Paths-tab, right click on the path and select "Path to selection". Using the Fill-tool, fill it with solid black. To soften the edges a bit, go to Filters -> Blur -> Gaussian Blur and set the blur radius to 5 pixels.

 

The iris
Now it's time to turn a boring, red circle into a detailed iris. Start by creating a new layer named "Clouds", and put it between the "Eye background" and "Pupil" layers. Fill the entire layer using the same red color that was used for the background, and open the "Difference clouds" filter (Filters -> Render -> Clouds -> Difference clouds). Check the "Turbulent" checkbox, and set the horizontal and vertical size to 8 pixels.

Next, go to Filters -> Distorts -> Polar coordinates. Set "Circle depth" to 100%, uncheck "Map backwards" and check the two other options. This wraps the pattern into a circle. There will be a seam where it wraps around, use the Clone tool to clean this up. And finally, select the background circle again, invert the selection and trim the "Clouds" layer.

Set the layer mode to "Subtract", and the opacity to 80%. It will probably look too dark, so go to "Colors -> Brightness & Contrast" to adjust it. I lowered the brightness by 100 and increased the contrast by 20 in this case, but feel free to experiment.

I wanted to create a "ring of fire" effect in the iris. For this, I made a new layer named "Ring temp", on top of the "Clouds" layer. Using the paintbrush tool, I drew a black vertical line. I then applied the "Wind" filter. Go to Filters -> Distorts -> Wind, set the style to "Wind", direction to "Left" and edge affected to "Leading". Threshold was set to 20 and Strength to 50. After that, apply the same filter again, but this time, set direction to "Right".

To turn this strip into a ring, first rotate the layer 90° clockwise (Layer -> Transform -> Rotate 90° clockwise) and then apply the Polar Coordinates filter, like was done with the "Clouds" layer. Next, select the ring by right clicking on the layer and selecting "Alpha to selection".

Select the Scale tool, and set it to "Scale selection". I made the selection about twice as big. Delete the "Ring temp" layer, and make a new layer "Ring", below the "Clouds" layer. Next, I enlarged the selection by 5 pixels (Select -> Grow) and filled it using orange (RGB color #ff9200).

Finishing the pupil
At the moment, the pupil is just a black almond shape. First, I'm gonna give it a dark red outline. I made a new layer named "Pupil shadow", right below the "Pupil" layer. I selected the pupil (right click layer -> Alpha to selection), expanded it by 10 pixels and filled it with dark red (RGB color #960000). I applied Gaussian blur (Filters -> Blur -> Gaussian blur) with a radius of 10 pixels, and set the opacity to 70%.

Next, I made a glow effect around the pupil. Again, a new layer, named "Pupil glow", right on top of the background. I selected the pupil, expanded it by 50 pixels and filled it using a lighter shade of orange (RGB color #ff3100). I then applied Gaussian blur with a radius of 20 pixels and set the layer mode to "Dodge".

Making it 3D
The following steps turn the eye from a flat image into a spherical, 3D-image. The first step: an inner shadow. Very easy. Create a new layer named "Inner Shadow", below the "Outline" layer. Select the eye background, and fill the "Inner Shadow" layer using dark red (RGB color #960000). Next, shrink the selection by 50 pixels, feather it by the same amount (Select -> Feather) and delete the selection. Set the layer mode to "Opacity" and you get a nice dark red inner shadow.

The next step is adding an inner glow to the top half of the eye. Create a new layer named "Inner Glow" right below the "Inner Shadow" layer, and select the eye background. Now select the ellipse select tool, and set the mode to "Intersect with current selection". Draw an elliptical selection from the top left corner to one grid division below the center of the eye.

Set the foreground color to pure white and select the Gradient tool. Set the gradient type to "FG to transparent" and the shape to "Radial". Reverse the gradient, so it goes from transparent to white, and draw the gradient from the top of the pupil, straight down to two grid divisions below the selection.
Set the opacity to 50%, the layer mode to "Grain merge" and apply Gaussian blur with a radius of 10 pixels to soften the edges, and you've got yourself an inner glow!

And finally, there's one finishing touch. Make a new layer named "Specks", below the "Outline" layer. Using the Ellipse Select tool, draw a small circle, and with the Gradient tool, using the same settings we used for the inner glow, draw a gradient from the top right to the bottom left. I made two specks of reflected light like this. The layer opacity is set to 70%, and Gaussian blur with a radius of 5 pixels is applied.

Finished!
Here's the eye I made, printed and glued to a 35 mm glass dome. If you want to print this, you'll probably have to adjust the brightness and contrast so the colors turn out right when printed. Also, use good quality photo paper, it makes all the difference in the world.

The method I explained here leaves lots and lots of room for experimenting. You can try different colors, layer effects, distortions, textures, ...