 Introduction  Illustration Techniques  Automatic Shading Model  Conclusion and Future work  Demo

 Method to automate some technical illustration conventions.  Technical illustrations: in textbooks, reference books, manuals i.e. a car owner’s manual.  Method: a shading algorithm based on edges, highlighting and cool-to-warm tones.

 Communication of geometry and form is more important than aesthetics or realism.  Edge lines are usually emphasized.  Important three-dimensional properties are preserved while extraneous detail is diminished.  Shadows are usually not included  Only one light is usually used

 Observed illustration characteristics: › edge lines, the set containing surface boundaries, silhouettes, and discontinuities, are drawn with black curves. › objects are shaded with intensities far from black or white with warmth or coolness of color indicative of surface normal; › a single light source provides white highlights. › shadowing is not shown.

 Subjects can infer at least as much geometric information from edge lines in drawn images verses shaded or textured images.  Hue changes are used to indicate surface orientation rather than reflectance.

 Automate the mentioned illustration characteristics. › Edge lines are drawn in black (mention in other paper) › Highlights are drawn using traditional term from the Phong shading model. › Shade the surfaces of objects

 Traditional diffuse shading method calculates luminance as follows:  Tone-based shading  Shading metal Objects

 kd = 1, ka = 0  The image hides shape and material information in the dark regions.

 Additional information can be provided by highlights (direction of light) and edge lines (divisions). Image produced by adjusting kd and ka

 Combining the shaded and illustrated model.  Poor image and loss of detail, not automated.

 Tones : color scales created by adding grey to a certain color.  Tones are important to illustration, especially when restricted to a limited luminance range.  Temperature : used to give depth cue. Warm colors advance, cool colors recede. › Warm – red, orange, yellow › Cool – blue, violate, and green › Temperate – red-violets, red-greens

 Tone for a pure red object: sum blue-to- yellow and dark-to-red to tone.

 Generalize the classic shading model to experiment with tones using the cosine term:  Use blue and yellow as two temperature extremes:

 Combining luminance shift (traditional shading), tone and temperature based shading. b = 0.4, y = 0.4, = 0.2, and = 0.6

 The different values of b and y determine the strength of the overall temperature shift, where as alpha and beta determine the prominence of the object color, and the strength of the luminance shift. b = 0.55, y = 0.3, = 0.25, and = 0.5

 Technical illustrators use a different technique to communicate whether or not an object is metal.  Illustrators represent a metallic surface by alternating dark and light bands.  Method: map a set of twenty stripes of varying intensity along the parametric axis of maximum curvature.

 Phong vs metal-shading

 metal-shading with edge and cool-to-warm shift

 An automated technical illustration method is presented using edge lines, highlighting, color-shifts and metal- shading.  Improvements in illustration rules  Automate other illustration forms  Interactive illustration