UV mapping is the 3D modeling

3D modeling

In 3D computer graphics, 3D modeling is the process of developing a mathematical representation of any three-dimensional surface of object via specialized software. The product is called a 3D model...

 process of making a 2D image representation of a 3D model.

UV mapping

This process projects a texture map

Texture mapping

Texture mapping is a method for adding detail, surface texture , or color to a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Dr Edwin Catmull in his Ph.D. thesis of 1974.-Texture mapping:...

 onto a 3D object. The letters "U" and "V" are used to describe the 2D mesh because "X", "Y" and "Z" are already used to describe the 3D object in model space.

UV texturing permits polygons that make up a 3D object to be painted with color from an image. The image is called a UV texture map, but it's just an ordinary image. The UV mapping process involves assigning pixels in the image to surface mappings on the polygon, usually done by "programmatically" copying a triangle shaped piece of the image map and pasting it onto a triangle on the object. UV is the alternative to XY, it only maps into a texture space rather than into the geometric space of the object. But the rendering computation uses the UV texture coordinates to determine how to paint the three dimensional surface.

In the example to the right, a sphere is given a checkered texture, first without and then with UV mapping. Without UV mapping, the checkers tile XYZ space and the texture is carved out of the sphere. With UV mapping, the checkers tile UV space and points on the sphere map to this space according to their latitude

Latitude

In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

 and longitude

Longitude

Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

.

When a model is created as a polygon mesh

Polygon mesh

A polygon mesh or unstructured grid is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling...

 using a 3D modeler, UV coordinates can be generated for each vertex

Vertex (geometry)

In geometry, a vertex is a special kind of point that describes the corners or intersections of geometric shapes.-Of an angle:...

 in the mesh. One way is for the 3D modeler to unfold the triangle mesh at the seams, automatically laying out the triangles on a flat page. If the mesh is a UV sphere, for example, the modeler might transform it into a equirectangular projection

Equirectangular projection

The equirectangular projection is a very simple map projection attributed to Marinus of Tyre, who Ptolemy claims invented the projection about AD 100...

. Once the model is unwrapped, the artist can paint a texture on each triangle individually, using the unwrapped mesh as a template. When the scene is rendered, each triangle will map to the appropriate texture from the "decal sheet

Decal

A decal or transfer is a plastic, cloth, paper or ceramic substrate that has printed on it a pattern or image that can be moved to another surface upon contact, usually with the aid of heat or water. The word is short for decalcomania...

".

A UV map can either be generated automatically by the software application, made manually by the artist, or some combination of both. Often a UV map will be generated, and then the artist will adjust and optimize it to minimize seams and overlaps. If the model is symmetric, the artist might overlap opposite triangles to allow painting both sides simultaneously.

UV coordinates are applied per face, not per vertex. This means a shared vertex can have different UV coordinates in each of its triangles, so adjacent triangles can be cut apart and positioned on different areas of the texture map.

The UV Mapping process at its simplest requires three steps: unwrapping the mesh, creating the texture, and applying the texture.

Finding UV on a sphere

UV coordinates represent a projection of the unit space vector onto the xy-plane.

See also

• UVW mapping
• Texture mapping
  Texture mapping
  Texture mapping is a method for adding detail, surface texture , or color to a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Dr Edwin Catmull in his Ph.D. thesis of 1974.-Texture mapping:...
  
  
• NURBS
• Polygon mesh
  Polygon mesh
  A polygon mesh or unstructured grid is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling...
  
  
• Mesh parameterization
  Mesh parameterization
  Given two surfaces with the same topology, a bijective mapping between them exists. On triangular mesh surfaces, the problem of computing this mapping is called mesh parameterization. The parameter domain is the surface that the mesh is mapped onto....
  
  
• Sculpted prim
  Sculpted prim
  A sculpted prim is a Second Life 3D parametric object whose 3D shape is determined by a texture. These textures are UV maps that form the rendered 3D sculpted prim...
  
  
• Least squares conformal map
  Least Squares Conformal Map
  A Least squares conformal map is a 2-D representation of a 3-D shape created using the Least Squares Conformal Mapping Method. By using the map as a guide when creating a new 2-D image, the colors of the 2-D image can be applied to the original 3-D model.LSCM is used in computer graphics as a...
  
  
• Cartographic projection

External links

• LSCM Mapping image with Blender
  Blender (software)
  Blender is a free and open-source 3D computer graphics software product used for creating animated films, visual effects, interactive 3D applications or video games. The current release version is 2.60, and was released on October 19, 2011...
  
  
• Blender UV Mapping Tutorial with Blender
  Blender (software)
  Blender is a free and open-source 3D computer graphics software product used for creating animated films, visual effects, interactive 3D applications or video games. The current release version is 2.60, and was released on October 19, 2011...