A better idea is to add big volumes in the normal map (the second example in the image above).
Something like in the picture below will work better. Just calculate a normal map between a plane and a blobby surface like the one below and overlay it in Photoshop in the normal map texture for the hair. This way you will have more variation in the surface direction and with a proper specular and transparency map a simple plane will look much better.
That pretty much cover all I wanted to include in this tutorial.
In the next paragraph I will show you the textures and geometry I used for Varga.
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Here is the final version of the hair.
Click images to enlarge.
The final geo has around 800 triangles and it's a mess.
These are the textures for the hair geometry (Diffuse, Normals, Specular in this order):
And below are the textures for the head; remember to treat the hair on the head geometry in the same way regarding color/specular (same colors/brightness for the diffuse and specular textures). If the head geo will be covered by the alpha planes this does not mean that you will have to skip detailing the head geo... there will be places where the hair geo will not cover entirely the head geo so the details on the head will be visible.