The term “graphics scene” is used to mean a set of graphics objects displayed on a screen, often for the purpose of interacting with a user, e.g. in the context of a video game or of a man-machine interface. The term “graphics object” is used to mean a synthetic object, i.e. an object defined by a set of parameters (shape, color, texture, . . . ) as contrasted with an object referred to as a “natural” object.
The images of the scene are for playing back the image in relief on a screen, regardless of whether the screen is or is not a three-dimensional screen.
Two-dimensional screens are used for displaying data in two-dimensional mode: a single image is displayed on the screen which plays it back without relief, however the image may optionally include an impression of depth that can be thought of as relief.
Three-dimensional screens, in particular stereoscopic three-dimensional screens for computers or TV sets, are commonly used for viewing data in relief. Three-dimensional screens are generally capable of displaying images in two-dimensional mode or in three-dimensional mode. In three-dimensional mode, two images are displayed by the screen which thus plays them back in relief. The two so-called “stereoscopic” images are offset relative to each other, one being for the left eye and the other for the right eye of a user of the screen. This offset, which is also known as parallax, corresponds to the difference in horizontal distance between the two eyes of the human user. Depending on the value of this parallax, the user's brain imagines a point of convergence situated in front of or behind the plane of the screen, thus associating an impression of depth with the observed object.
Other systems, and in particular multiple view systems, also known as multi-view systems, generate more than two images of the screen, which images correspond to different views of objects for displaying in a plurality of directions. A plurality of images are then transmitted to a screen, referred to as a “multiscopic” screen, thereby enabling the scene to be viewed in relief at a plurality of different viewing angles. Depending on the user's position relative to the screen, the user can then benefit from two of the available images in order to construct a stereoscopic view of the image.
Usually, graphics scenes rely on a set of graphics software libraries (also known as “a graphics toolkit”) that serve to draw the basic graphics components, e.g. cubes, polygons, buttons, lists, etc. Graphics libraries can communicate directly with the hardware of the terminal, in particular a video memory, a video card, and a graphics processor unit (GPU), or may make use of a graphics driver program (or application program interface (API)) in communication with the hardware.
Whatever the type of screen used, it is generally assumed that the user is located at a distance and in a position that are constant. Nevertheless, it is becoming more and more frequent that the user moves in front of the screen, in particular when the user is playing a game. This movement gives rise to drawbacks.
For example, in prior art solutions, the user cannot benefit from information about the hidden faces of the object (top, bottom, or sides of the object).
Furthermore, the inventors have found that those solutions generate stereoscopic images of quality that is poor since one of the images is not necessarily in register with the other. Specifically, prior art solutions assume that the user's head is held upright, and thus that the axis between the two eyes is parallel to the horizon line. If this is not true, then the user loses accuracy in stereoscopic viewing.