Basic Approaches for Visible Surface Determination

There are two basic approaches for visible-surface determination, as per if they deal along with their projected images or along with object definitions directly. These two approaches are termed as image-space approach and object-space approach, correspondingly. Object space processes are implemented in the physical coordinate system wherein objects are explained whereas image space processes are implemented in screen coordinate system wherein the objects are viewed. In both cases, we can imagine of each object like comprising one or more polygons as or more complicated surfaces.