For the entire project I used Maya as 3d application, Photoshop for texture painting and Mudbox for high resolution. For the hair I used Maya paint effects a lot in the past ... now i like to paint the hair in Photoshop, it gives me more freedom and variation using custom brushes and a little more time. You can customize some paint effects brushes in Maya to do the trick and I will show you later how to do it.
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3.2. Painting the hair texture:
The most important thing when painting hair textures with alpha is the alpha channel (basically the transparency map). You should put more effort in painting the form and irregularities of hair strands and then concern about light and shadow in the diffuse texture.
I will nail down two approaches for painting the alpha for the hair:
-Maya paint effects
Maya paint effects:
The first approach that I used a lot in the past and did the job well is using Maya paint effects. With a little effort and a few hours of work you can make some pretty good fx brushes for painting hair, I have a few custom ones done by myself but I will start from a basic one to show you the process.
This is Maya paint effects canvas:
Click on the brush presets icon and the visor will pop up. From the paint effects tab inside visor choose the "hair" folder and then the most saturated red hair there like in the picture below. You can play with other presets as you like but this one is best suited for what i need.
If you are using a Wacom tablet you can map the pen pressure to different attributes of the brush in the paint effects tool settings dialog .
This is how the default brush will look like (hit the alpha channel button shown in the paint effects canvas picture to work only with alpha).
Now to customize the brush hit Ctrl + b to open the Paint Effects Brush Settings dialog box. Here you can find all the parameters you will have to modify to customize the brush and there are plenty (I did not count them but I remember in a tutorial saying that there are more than a hundred parameters for paint effects brush settings ).You will not have to play with all of them ... but some are quite useful.
Pay attention to the brush profile parameters, especially Brush Width and Stamp Density.
Also under the Tubes section you will find Creation and there you have Tubes per step which modify the density of the tubes, the segments attribute (which you will have to increase if you have curly hair) (tip: you can enter a bigger value than the maxim allowed when you drag any slider by numerically entering the value in the field).
You can also modify some parameters in the Tubes->Behavior to alter the behavior of the brush.
In the Forces sections you can modify Path Follow so that the tubes will closely follow the path if you draw curved strokes and add randomness to the tubes using Random parameter.