Hidden surface determination
The visibility problem is when rendering in computer graphics, the question of which are visible portions of surfaces in a 3D scene with the projection on the two-dimensional display surface. When masking calculation or a visibility determination procedure is accordingly called, are detected and sorted out with the non- visible surfaces and so the visibility problem is solved. The visibility problem was one of the first major problems of computer graphics.
The masking calculation is necessary for correct rendering of a 3D scene, because surfaces that are not visible to the viewer, also should not be shown. Many methods also accelerate the rendering because visible surfaces can not be excluded from further processing by the graphics pipeline.
Method
After Ivan Sutherland concealment algorithms for computation in object space method, image space method and list - priority process can be divided. While in the object space method, the visibilities are calculated directly from the objects analytical and independent of the output device in the image space method, the masking calculation for each individual image or pixel position is carried out separately. List priority algorithms first compute a reference to the objects visibility order, or " priority " in advance and then dye the pixels of the image; So they work partly in the object and in the image space.
Today's graphics hardware uses to conceal calculation usually a Z-buffer; in realistic image synthesis ray tracing is often used.
For a related problem see visibility polygon.