Textures and Shaders

Textures and shaders are two components of what make up a 3D model. The better the textures and shaders the better it's going to look. A prime example is the use of texture and shader packs in minecraft.

It goes from this:

To this:

Textures

Textures are images that define not only what the mesh of your 3D model looks like but also helps to refine the many attributes in a Shader. 

How do we apply a 2D image/painting to a 3D model?

First the model needs to be unwrapped. This is done through UV unwrapping which is a tedious task that must be done. The best example of this is unwrapping a cube and instead of describing what happens I'm just going to post a picture that should give you an idea of what unwrapping is as this post is not about UV unwrapping.

So now that I've gotten that out of the way back to texturing. As I said textures are a 2D image applied to a 3D model. There are three main map types used in texturing: Colour/Diffuse Maps, Specular and Bump Maps and Displacement or Normal Maps.  

Colour/Diffuse Maps are the basic texture maps that, well, as the name suggests add the colour and texture to the model. This could be the grain of wood on a crate or on a larger scale the scales of a dinosaur. 

Specular Maps add shine and gloss through the highlights on a specular map. The software reads the areas painted on the map to apply different levels of specularity to the object. This helps to give it a more 3D look and to give more dimension and texture to metal, glass or plastic surfaces.

Bump Mapping gives a 3D feel to a 2D surface. Yes, I know, giving a 3D feel to a 2D surface is the whole point but let me explain this. A bump map gives the appearance of an extrusion or indentation to the 2D surface without having to use polygons on the 3D model to make those extrusions or indentations. This can be used to create the indentations between bricks on a wall or the bumps on industrial steel sheets. Normal maps are pretty much the same thing but instead of using a B&W colour scale it uses an RGB colour scale.

While those are the three main types of texture maps there are two others that are used regularly:

• Reflection Map: This map simply tells the software which parts of the 3D model should be reflective. These maps are in B&W colour scale with black indicating no reflectivity and pure while 100% reflectivity.
• Transparency Map: Just like a reflection map except instead of reflectivity it tells the software which parts should be transparent and how transparent they should be. 

Shaders

Shaders communicate with the rendering engine on how the 3D model should interact with light. Without the shader the model would not appear in the render as there would be no instructions for the render engine on how to display it on screen.

Different types of shaders are used to represent different types of surfaces. E.g. A glossier surface would require a different shader to a cloth surface.

There are three generic shaders: 

• Lambert: more 'diffuse' than the other two generic shader types which means that light is scatter evenly across the surface rather than being directly reflected. This shader gives the surface the same brightness regardless of the angle it is viewed from. E.g. roughly cut wood.
• Blinn/Phong: Whilst only slightly different Blinn or Phong shaders are usually used for reflective surfaces like metals.  These shaders have  a strongly defined specular highlight which gives the impression of glossiness or shine.
• Anisotropic: This shader also shows a distinct highlight but with the reflection appearing as an elongated ellipse as opposed to the other two which are isotropic. Anisotropic surfaces typically have a directional grain that causes long, repeated highlights like hair or glass.

These shaders have a set of base parameters that can be customised to meet specific needs and it's very rare that a generic shader will perfectly satisfy the aesthetic goals of the artist without some sort of modification.

References

Delrio, J. (2011). Components of a 3D model | 3DVIA Blog. 3dvia.com. Retrieved 4 July 2014, from http://www.3dvia.com/blog/components-of-a-3d-model/

Slick, J. (2014). Surfacing 101 - Shader Networks & Surface Materials. About.com 3D. Retrieved 4 July 2014, from http://3d.about.com/od/Creating-3D-The-CG-Pipeline/a/Surfacing-101-Shading-Networks-And-Surface-Materials.htm

Slick, J. (2014). Surfacing 101: How Texture Maps Are Made. About.com 3D. Retrieved 4 July 2014, from http://3d.about.com/od/3d-101-The-Basics/a/Surfacing-101-Texture-Mapping.htm