Figure 1: Left: Phong-shaded model. Right: Cool to warm shading, including silhouettes and creases as used by technical illustrators.

  

Figure: Three line conventions suggested by Martin [14]. Left: single weight used throughout the image. Middle: heavy line weight used for outer edges, other lines are thinner. Right: vary line weight to emphasize perspective.

  

Figure: Left: Illustrators sometimes use the convention of white interior edge lines to produce a highlight. Image copyright 1995 Macmillan [20]. Used by permission. Right: An image produced by our system, including shading, silhouettes and white crease lines.

    

Figure 4: The dark banding in the light splash back model can communicate more curvature information and works well on organic models.

  

Figure 5: Left: Model with cool to warm shading with lights positioned up and to the right. Middle: After the camera position is moved to view the side of the model. Right: After moving the object instead of the camera, allowing the surface to vary completely from cool to warm.

  

Figure 6: Metal-shaded object with shadow and ground plane. White creases and black silhouette lines are also drawn.

   

Figure 7: Adding the silhouettes to the environment map instead of calculating silhouettes from the geometry produces interesting artistic effects.

  

Figure 9: All creases are drawn in white (Left), and then all of the silhouette lines are drawn in black (Right), overlapping the creases.

  

Figure 10: Shaded sphere images used for environment maps.

Figure 11:

Drawing the shadow of a sphere with a spherical light source directly onto a ground plane directly below it, traditionally each sample will render an ellipse. To get an accurate representation of the penumbra, this surface of the spherical light source needs to be sampled in 2 dimensions. With our method, each shadow is a concentric circle, requiring less samples to get the same results.

  

  

Figure 12: Shadows provide valuable information about three dimensional structure, especially the spatial layout of the scene

a) Hard penumbra and hard umbra. b) Single hard, colored shadow. c) Colored soft shadow