The process of applying two-dimensional images onto the surface of a three-dimensional object is called UV mapping. UVs themselves are textures that co-ordinate with vertex component information (Pluralsight, 2014) – existing to define a two-dimensional texture co-ordinating a system called “UV texture space,” using the letters U and V to indicate the axes in 2D (Autodesk, 2017), with U corresponding to horizontal or latitude and V to vertical or longitude. These co-ordinates control the placement of the points on the image texture to that of the surface mesh, and are assigned to every vertex, and are known as texture coordinates (Chopine, 2012, p. 153).
Retrieved from Chopin, 2012, p.154.
In a polygon surface type (which is most common amongst 3D modelling programs) UVs atypically exist by default, and must be created and/or subsequently modified so that the surface mesh adapts to the texture map (Autodesk, 2017).
To actually apply the images, a polygonal face must be allocated a set of UV co-ordinates from the image plane in a process called unwrapping. The UV coordinates are visually exported into a square bitmap image that varies in size, which is then used as a layout for the texture files (Slick, 2016).
The process of unwrapping.
Retrieved from http://goanna.cs.rmit.edu.au/~gl/teaching/Interactive3D/2012/lecture9.html (18/02/17)
Creating the UV Layout:
Projection of the UV layout can be applied to selected faces using two methods, (depending the shape of the object) planar projection or cylindrical projection, (Slick, 2016).
- Flat surfaces make use of the planar projection technique, where the image is applied directly to one face. This can flatten all the way through the model, so objects with multiple faces would have UVs stacked over each other.
- Curved surfaces make use of cylindrical projection which wraps around the entire object. Artists change the object manually as most surfaces are projected automatically.
In basic terms, the image texture maps are placed on a 3D object using a process called UV mapping. This process correlates the image and its appearance when mapped onto a 3D object.
The UVs themselves are the co-ordinates, whilst their placement is administered by a co-ordinating system called the UV Texture Space. UVs appear as a flattened image, representing the texture to be placed on the surface mesh. This skill is crucial for mapping realistic textures onto polygonal surfaces.
Some other 3D applications and plugins (e.g. Mudbox) allow artists to paint directly onto 3D objects without unwrapping, with the application automatically setting up the UV co-ordinates in correlation to the texture (Chopine, 2012, p. 157).
Autodesk, (2017) Introduction to UV Mapping. Retrieved from https://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2015/ENU/Maya/files/UV-mapping-overview-Introduction-to-UV-mapping-htm.html
Chopine, A. (2012) 3D Art Essentials: The Fundamentals of 3D Modeling, Texturing, and Animation. Focal Press.
Pluralsight, (2014) Understanding UVs – Love Them or Hate Them, They’re Essential to Know. Retrieved from https://www.pluralsight.com/blog/film-games/understanding-uvs-love-them-or-hate-them-theyre-essential-to-know
Slick, J., (2016) Surfacing 101: Creating a UV Layout. Retrieved from https://www.lifewire.com/creating-a-uv-layout-1955