OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Per-Primitive Antialiasing

You might have noticed in some of your OpenGL images that lines, especially nearly horizontal and nearly vertical ones, appear jagged. These jaggies appear because the ideal line is approximated by a series of pixels that must lie on the pixel grid. The jaggedness is called aliasing, and this section describes one antialiasing technique for reducing it. Figure 4.3 shows two intersecting lines, both aliased and antialiased. The pictures have been magnified to show the effect.

Figure 4.3. Aliased and antialiased lines

Figure 4.3 shows how a diagonal line 1 pixel wide covers more of some pixel squares than others. In ...