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After playing for some weeks with ZBrush, I wanted to do a small project.
To keep this short, Im going to assume for this tutorial that the reader is already
familiar with the basics of Mental Ray for Maya and ZBrush...
For fullsize result go to the gallery: http://highend3d.com/gallery/nature/green-sea-turtle-797.html

Texturing

Painting deformations in ZBrush, I presume, is a lot of fun with a graphic tablet. I tried this with a
mouse but just wasnt satisfied with my sculpting results, and so for the detailing I relied mostly
on deformations which were limited by alpha masking, and used bump mapping for smaller
details.

For this approach, properly laid out UV coordinates are required. With this approach it
makes sense to do the texture painting prior to the detailing in ZBrush. All colour texture maps
were 2D painted in Photoshop on top of UV snapshots. I painted in 2K and 3K resolution
and used plenty of reference images from the Internet and photographs that I took in a Beijing
aquarium. The UV mapped model (1 level smoothed) can be seen in Fig02, and UV maps
for all the body parts in Fig03.

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After finishing the colour maps, I painted, or extracted from the colour maps, greyscale
deformations and bump maps for features like the wrinkles and bumps that I wanted to model
in ZBrush. I used these maps to control the deformations in the ZBrush tool panel. When
used as an alpha mask the black areas of the mask kept the model unaffected, so the
deformations only changed certain parts of the model. For better control and a more irregular
look I painted separate maps for different features, and layered the deformations on top of
one another.

Sometimes I even used different maps for the positive and negative deformation
values. I imported the models into ZBrush and divided them six times. I then applied the alpha
masking, and mainly positive and negative values for Offset, Inflate, Spheres and Taper
deformations. For the small details and skin texture, a modified greyscale version of the
colour map was added as a bump map on top of it. This way, the generated details matched the
colour textures exactly. The head colour map can be seen in Fig04;

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some deformation alpha maps used for masking the neck in Fig05 - 06;

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deformation alpha maps used on the chin, and
the bump map for head details (based on the colour texture map), in Fig07 - 08.

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