detection, animation, morphing, and acceleration techniques using spatial subdivision schemes such as Quadtrees or Octrees. These are also used to reduce the amount of main memory required at a given time. The "world" of a modern computer game is far larger than what could fit into memory at once. Geometry The geometry step (with Geometry pipeline), which is responsible for the majority of the operations with polygons and their vertices (with Vertex pipeline), can be divided into the following five tasks. It depends on the particular implementation of how these tasks are organized as actual parallel pipeline steps. Definitions A vertex (plural: vertices) is a point in the world. Many points are used to join the surfaces. In special cases, point clouds are drawn directly, but this is still the exception. A triangle is the most common geometric primitive of computer graphics. It is defined by its three vertices and a normal vector - the normal vector serves to indicate the front face of the triangle and is a vector that is perpendicular to the surface. The triangle may be provided with a color or with a texture (image "glued" on top of it). Triangles are preferred over rectangles because their three points always exist in a single plane. The World Coordinate System The world coordinate system is the coordinate system in which the virtual world is created. This should meet a few conditions for the following mathematics to be easily applicable: It must be a rectangular Cartesian coordinate system in which all axes are equally scaled. How the unit of the coordinate system is defined, is left to the developer. Whether, therefore, the unit vector of the system is to correspond in reality to one meter or an Ångström depends on the application. Whether a right-handed or a left-handed coordinate system is to be used may be determined by the graphic library to be used. Example: If we are to develop a flight simulator, we can choose the world coordinate system so that the origin is in the middle of the earth and the unit is set to one meter. In addition, in order to make the reference to reality easier, we define that the X axis should intersect the equator on the zero meridian, and the Z axis passes through the poles. In a Right-handed system, the Y-axis runs through the 90°-East meridian (somewhere in the Indian Ocean).