【UV mapping】
UV mapping is the 3D modeling process of making a 2D image representation of a 3D model's surface.
This process projects a texture map onto a 3D object. The letters "U" and "V" denote the axes of the 2D texture 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,[2] 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. When a model is created as a polygon mesh using a 3D modeler, UV coordinates can be generated for each vertexin 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 anequirectangular projection. 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".