Figure 7

Generation of edge lines for pen-and-ink style drawings. (A) Edge lines for a tube are calculated by measuring the angle between the view vector V and the surface normal vector N, and then darkening a surface if the angle is close to 90 degrees. (B) The equation for edge-line intensity is based on the smooth function used for single-pass wireframe rendering [46]. (C) A tube style display of the human growth hormone protein [PDB:1HGU], a four α-helix bundle structure [47], is shown in gray scale and using Phong lighting with a single directional light and no specular highlighting. (D) Edge lines are added to the image shown in (C).