What is a Texture map?
A texture map is an image that is applied to an object in a game engine in order to give the engine information on how the object should be displayed when it is rendered. It is possible to sculpt the level of detail that is shown in a texture map directly onto a model, but this would drastically increase the number of polygons used on the 3D object, and therefore slow the game down. Texture maps allow you to fake this detail, whilst maintaining a low polycount.
Diffuse Maps (_DIFF)
A diffuse map is the original pixel colour information image. Applying a diffuse map to an object is essentially like applying a flat wallpaper with bricks on it to the side of a box. It looks realistic from a distance, but up-close it is obvious that it is not real. Other maps can help us mask the fact that the texture images is flat, by affecting the way that light hits the images, and which parts of the image are more reflective than others.
This is an example of a diffuse map:
Normal Maps (_NORM)
Normal maps are used to fake the 3D edges on a surface. The colours on a normal map correspond to the x, y, and z axis used in 3D programs. This allows the computer to read the positioning of the surface, in order to affect the way that light hits the surface of that object.
This is an example of a Normal Map:
Specular Maps (_SPEC)
Specular maps control the shinyness of the texture, in the range of colours black to white. The more white the pixel in the image is, the more shiny that part of the texture will be. For example, the same piece of plastic would have a different specular map when it is wet, compared to when it is dry.
This is an example of a Specular map:
Ambient Occlusion Maps (_AO)
Ambient Occlusion maps create soft shadowing on models that are not lit from a direct light source. Ambient occlusion maps are usually generated from model geometry, but more modern graphics cards can perform Screen Space Ambient Occlusion, which is real-time ambient occlusion. However, this can lead to shading errors.
This is an example of an Ambient Occlusion map:
Alpha maps give the computer data on a surfaces transparency. Alpha maps use a range of blacks, greys, and whites to show how transparent a surface is. Black surfaces are completely transparent, and white surfaces are completely opaque.
THis is an example of an Alpha Map:
Displacement Maps (_DISP)
Displacement maps physically displace the surface of an object in order to create detail on that surface. Unlike normal maps which fake details on a models surface, displacement maps actually move the geometry to create raised or lowered surfaces. The amount that the surface is raised or lowered depends on the value of the grey in the displacement map image.
This is an example of a Displacement Map:
Detail Maps (_DET)
Detail maps allow the creation of high-detail surfaces on large objects, such as environments. They are created using a combination of bump, diffuse, and normal maps, which are combined into the shaders of a texture map, but with a higher level of UV tiling, as to create smaller pixels. Using MIP maps alongside of them allows the detail to fade away as the player gets further away, in order to hide the fact that it is repeating.
Mip Map (_MIP)
Mip maps allow textures to be faded out as they get further away from the player. Textures close up will be full detail, but this will reduce as the textures get further away. This allows the textures further away to render properly, without pixelating or distorting.
This is what a mip map looks like on an environment:
Russell, E. (2014) Understanding the Difference between Texture Maps [online] Available from: http://blog.digitaltutors.com/understanding-difference-texture-maps/ [Accessed 11th April 2016]
Polycount (2016) Ambient occlusion map [online] Available from: http://wiki.polycount.com/wiki/Ambient_occlusion_map [Accessed 11th April 2016]
Polycount (2016) Transparency map [online] Available from: http://wiki.polycount.com/wiki/Transparency_map [Accessed 11th April 2016]
Russell, E. (2014) Know the Difference: Bump, Normal and Displacement Maps [online] Available from: http://blog.digitaltutors.com/bump-normal-and-displacement-maps/ [Accessed 11th April 2016]
Polycount (2016) Detail map [online] Available from: http://wiki.polycount.com/wiki/Detail_map [Accessed 11th April 2016]
Polycount (2016) Mip Mapping [online] Available from: http://wiki.polycount.com/wiki/Mip_Mapping [Accessed 11th April 2016]