Texturing can be a lot of fun; it’s a very creative process and you can take it as far as you want. Applying the textures is the point in the process when you really have the opportunity to make a character realistic. If you want realism, it’s recommended that you use photos to create your textures (skin, wood, grass, sand—virtually anything) instead of painting them manually. In Jim’s case, the style is not photorealistic at all, so some basic textures defining the colors and some details are fine.
Depending on the requirements of the texture, its effects can be very different. If it’s a diffuse color texture that will be mixed with other textures to define a surface’s shine or reflectivity for example, it will only have color information. However, if you’re working on a video game in which lighting is more technically limited, the texture will include highlights and even some shadows.
If you’re interested in how to create really cool textures, you might want to learn how to use a 2D image editor like Photoshop or Gimp. They’re really powerful and allow you to create awesome textures that will bring your characters to life!
3.133.108.103