Beginning in the 1990s platforming games began to transform from pseudo-3D to "true 3D" experiences, the distinction being constraints on the degree of control the player over the character and camera. Rendering of 3D environment from angles controlled by the user necessitates that the graphics hardware be sufficiently powerful, and that the art and rendering model of the game can be viewed from an arbitrary angle. The improvement in graphics technology allowed publishers to produce such games, but introduced several new issues; for example, if the virtual camera can be positioned arbitrarily, it must be constrained to prevent it from clipping through the environment.[23]