Visible surface determination

In order to display a three-dimensional scene, the visible objects must be determined. There are two aspects of such visibility considerations. First of all, clipping will remove all objects that are not in the range that the viewer can oversee. Rendering is only necessary for the objects inside the clipping region. Problems in connection with clipping for two-dimensional graphics have been discussed in chapters 3 and 4. Clipping for three-dimensional scenes will be slightly more complicated. However, there is an additional aspect which only occurs in the three-dimensional case. An object might be in the viewer’s viewing range, but it is invisible for the viewer since it is covered by other objects from sight. This chapter focusses on three-dimensional clipping and algorithms for determining visible objects.