Here is where I'll be starting:
"Many previous techniques exist for fast, automated outlines and
two-tone shading (e.g., [Markosian et al. 1997; Raskar and Cohen
1999; Gooch et al. 1998, 1999; Buchanan and Sousa 2000; Gooch
and Gooch 2001; McGuire and Hughes 2004])."
MARKOSIAN, L., KOWALSKI, M., GOLDSTEIN, D., TRYCHIN, S.,
AND HUGHES, J. 1997. Real-time nonphotorealistic rendering.
SIGGRAPH ’97, 415—420
RASKAR, R., AND COHEN, M. 1999. Image precision silhouette
edges. In Proc. of I3D 1999. 135—140
GOOCH, B., GOOCH, A., SHIRLEY, P., AND COHEN, E. 1998. A nonphotorealistic
lighting model for automatic technical illustration.
SIGGRAPH ‘98. 447—452
BUCHANAN, J., AND SOUSA, M. 2000. The edge buffer: a data structure
for easy silhouette rendering. Proc. of NPAR ’00, Annecy, Fr.39—42
GOOCH, B., AND GOOCH, A. 2001. Non-photorealistic rendering.
AK Peters, Natick, MA
MCGUIRE, M. AND HUGHES, J. 2004. Hardware-determined
feature edges. In Proc. of NPAR ’04. Annecy, Fr., 135—147