Take a look at Basic Mask Editing for that. Take a look at HP's Custom Pattern Tutorial for that.
Teach you how to alter the base textures of CAS parts in the Sims 3.Altering the base texture can turn bland boring opera gloves into beautiful tattoos like these. Whereas the base texture itself adds details to the CAS part like wrinkles and folds. The game uses the Alpha layer of the base texture to determine what parts of the texture you want displayed. Base textures can be thought of as the 'canvas' the game 'paints' the patterns and colors onto.
