First of all I need the UV texture map from Maya, to do this I simply go into Maya's UV Map window and go to Polygons>UV Snapshot and save the file as a tiff format image. I then import this file into Photoshop, this first thing you'll notice is the UV map is inverted, white lines on black, to solve this simply go to Image>Adjustments>Invert. Unlock the layer by double clicking on it and change it's mode from Normal to Multiply.
I next then set up each of the layers I'll need, these usually consist of:
- Base layer (This is where the base colours go, Layer mode: Normal)
- Shadows (Layer Mode: Multiply)
- Highlights (Layer Mode: Normal, w/adjuseted Opacity on Layer or Brush)
- Texture (Layer Mode: Overlay)
You might also be wondering why the texture layer uses the Overlay mode rather than Multipy. This is because by using Multiply the whole image is present and only the white and lightly coloured sections will become transparent. Overlay does pretty much the same as Multiple but without such drastic effects happening to the lighter coloured areas. If you find that Overlay isn't quite doing it try Softlight instead.
To the left you can see a texture in the process of being made, notice that this texture has more than one UV map on it. In these types of situations. It best to keep your layers organised in to folders (such as the ones seen in the top image) again this helps reduce and complications whilst painting textures.
When it comes to painting the shadows section, I use the method I learned from the book 3D Game Textures. With the Shadows Layer selected I first use a larger brush (w/ around 13% on the brush) with a darkish grey and paint around the edges of the mesh, I then use a smaller brush (w/ 24%) with a darker grey and follows the mark made previously, finally I use an even smaller brush (30-46%) with the darkest grey I paint around the adges whilst higging the line of the UV map.
Lighting is done in the same way to the last step of the shadow painting with the exception that the brush's Opacity is around 18% as to not over power the image itself. You can see an example of this final texture on the mesh below.
Althogether thats good summerisation of the processes I used when it came to painting the textures in my game level. Over the course of this project I've learned so much about the whole process of not just texture painting but UV mapping as well.