A texture atlas is a 2D image with multiple textures or images used in computer graphics programming to save resources. In 3D graphics, it contains the entire image intended to be textured on a given 3D object. UVW mapping is used to create a texture atlas. It saves system resources and increases rendering speed. However, precision is required when creating it by hand.
In computer graphics programming, a texture atlas is a two-dimensional (2D) image with multiple textures or multiple images within the main image that can be extracted and used by the main application to save resources that would otherwise be used to load and keep every single image or texture. In three-dimensional (3D) computer graphics, a texture atlas is slightly different in that it contains the entire image intended to be textured on a given 3D object, but that image is organized in a sometimes confusing and distorted way, with individual faces of each polygon in the 3D model plotted flat on the 2D image. Some programming languages, graphics libraries, and even hardware have some system overhead associated with using a single image. Combining multiple images into a single sheet, or texture atlas, allows a program to reduce overhead at the expense of additional computer code and, possibly, processing time to draw subsections of the atlas on the surfaces that require them.
When used in 3D computer graphics, a texture atlas is the result of a process known as UVW mapping. The letters UVW are not an acronym but are references to texture coordinates and are used to avoid confusion with the more standard X, Y and Z coordinates used for scene geometry. If a 3D model will use UVW mapping, each of the polygons is first flattened to create a 2D image, with each polygon remaining connected to neighboring polygons. The resulting texture atlas—all of the 3D model’s polygons arranged flat, a process sometimes called unrolling—can then be used as a template to ensure accurate placement of images on the various surfaces of the object.
In 2D applications, a texture atlas can save system resources and time spent loading the image, and increase rendering speed by reducing the amount of work a graphics card has to do to quickly switch images. A 2D texture atlas can be used for a graphical user interface (GUI) where each of a button’s images are within the same image, in a grid pattern. This way, whenever you need to render a button image on screen, you can draw the larger image subsection instead of having to move memory locations first or load the individual texture into graphics memory.
One complication with using a texture atlas is the amount of precision required if the atlas is created by hand. For an application that uses 32 pixel wide tiles, the atlas needs to have each tile aligned exactly in 32 pixel increments, which can be time consuming and tedious. Many times, programmers will use some kind of utility software to take a batch of individual images and build the atlas procedurally, eliminating the need to count pixels in a paint program.
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