What is a ball mapping?
In computer graphics, the mapping of the sphere can refer to one of two methods used to apply an image or procedural texture to a three -dimensional (3D) sphere. Generally, the ball mapping is used to apply a two -dimensional (2D) rasterized image to the ball surface and distorts the flat image to match the polar coordinates. The mapping of the sphere is also used to describe the form of environmental mapping, which uses a pre -drawn image of the scene that is mapped to the surface of the ball in a way that causes the ball to reflect the environment around it, as a ball made of perfectly reflective metal. Both types of ball mapping results in a three -dimensional ball that has a texture applied to its surface, although the environmental mapping disrupts the image in a different way than the mapping of spherical projection.
When using a texture on the shape of the ball, the mapping of the sphere takes 2D picture and projected itto the surface of the sphere with texture. The picture follows the coordinate system of the ball, where each peak on the surface is similar to the intersections of length and latitude in the world. This means that as the image reaches the poles of the ball on the upper and lower parts, the image begins to squeeze towards a single peak and effectively distorts the image. In many cases with a properly created texture image, this gives the sphere a more natural look, unlike mapping cube mapping or cylinder mapping. This technique is used to create graphics and animations of textured spheres, such as planet Earth with satellite images of oceans and continents.
When using the environment mapping, the ball mapping is a quick way to create an object that seems to have a mirror surface. The process calculates the light vectors from the ball surface, and this vector is then translated into the coordinals that are used to find the color in the 2D image. Unlike the mapping of projections of the sphere, the reflective version disrupts the image in a somewhat different way.
One of the advantages for using the environmental mapping is that it is very fast compared to other methods, such as tracing beams that dynamically calculate the reflection based on objects in the scene. The method is fast because the reflection is actually a pre -rendered picture. This leads to some complications with technology because dynamic changes in the environment or objects that move in the scene will not be displayed in the reflection. In addition, because perceived reflection is static, concave shapes that receive mapping will not be reflected, which sometimes causes confusing visual effect.