Simulating cel animation and shading

Details Simulating cel animation and shading Simulating cel animation and shading

1996-06-28

1999-10-12

Zimmerman, Mark K.

Computer graphics processing and selective visual display system

Computer graphics processing

Graph generating

345426, 345441, G29G 502

Patent

active

059661348

ABSTRACT:
A cel image is rendered by a computer to have a "toon" look that simulates a traditional hand-drawn cartoon cel. The toon appearance of a cel image is characterized by the use of areas selectively colored with a fill, a highlight, or a shadow color. The present invention uses a material shader modified to return a value defining the color applied to each area in the scene being rendered as a function of a predetermined highlight threshold angle, which is compared to the angle of each light ray intersecting surfaces in the image. An edge detection convolution filter is applied to define color lines between the different color areas in the colored image. Contour lines defining the shape of an object and lines on its interior surfaces are determined by applying an edge detection convolution filter to surface normal data for the colored image. Additional smoothstep or gain filters may be applied to improve the contrast of the color lines and contour lines and to thicken the color lines. To avoid aliasing artifacts, the colored image is rendered at from two to four times the resolution of the cel image that is ultimately desired, and the pixels of a composite image produced using the colored image, color lines, and contour lines are averaged down to obtain the desired resolution of the cel image.

REFERENCES:
patent: 5583975 (1996-12-01), Naka et al.
patent: 5621868 (1997-04-01), Mizutani et al.
patent: 5668940 (1997-09-01), Steiner et al.
Foley et al.; "Computer Graphics: Principles and Practice"; pp. 132-142, 606, 744-745, 1996.
Carmona, Jeff; "Animation packages let educators explore new dimensions"; The Journal (Technological Horizons in Education) v.22, n. 5, p. 12(4), Dec. 1994.
Martinez, Carlos Domingo; "Elecriclmage Animation System 2.0"; Macworld v. 11, n. 12, p. 59 (1), 1994.
Forcade, Tim; "Mimic real-world shadows with color and animation"; Computer Graphics World, v.17, n. 12, p. 59(3), Dec. 1994.

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