US 5,966,134 A · Simulating cel animation and shading

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.

Claims30

Dependent claims

A method for automatically producing a cel image that simulates a hand-drawn animation cel, comprising the steps of:

(a) using a computer, rendering a colored image, said step also producing surface normal data for surfaces in the colored image;
(b) when rendering the colored image, comparing a predetermined threshold angle with angles at which light rays intersect with surfaces in different portions of the rendered image to determine which of a plurality of predefined colors are applied to the surfaces;
(c) creating color lines in the colored image that delineate differently colored portions of the colored image by detecting edges between the differently colored portions along which the color lines are extended;
(d) creating contour lines that follow an outline of an object in the colored image and which define any curves on any interior surfaces of the object by detecting edges in the colored image as a function of the surface normal data;
and
(e) compositing the colored image, the color lines, and the contour lines to produce the cel image, said color lines and contour lines simulating outlining in the cel image of a corresponding animation cel and said predefined colors applied to the different portions of the colored image simulating paint colors applied to the corresponding animation cel.

3 more elements

A system for automatically producing a cel image that simulates a hand-drawn animation cel, comprising:

(a) an electronic display;
(b) a memory for storing a machine instruction comprising a software program and data required by and produced by the software program;
and
(c) a processor coupled to the memory that is controlled by the machine instructions to implement a plurality of functions when executing the software program, said functions including:
(i) rendering a colored image, and while doing so, producing surface normal data for surfaces in the colored image;
(ii) when rendering the colored image, comparing a predetermined threshold angle with angles at which light rays intersect with the surfaces in different portions of the rendered image to determine which of a plurality of predefined colors are applied to the surfaces;
(iii) creating color lines in the colored image that delineate differently colored portions of the colored image by detecting edges between the differently colored portions along which the color lines are extended;
(iv) creating contour lines that follow an outline of an object in the colored image and which define any curves on any interior surfaces of the object by detecting edges in the colored image as a function of the surface normal data;
and
(v) compositing the colored image, the color lines, and the contour lines to produce the cel image, said color lines and contour lines simulating outlining in the cel image of a corresponding animation cel and said predefined colors applied to the different portions of the colored image simulating paint colors applied to the corresponding animation cel.

7 more elements

An article of manufacture adapted for use with a computer, for automatically producing a cel image that simulates a hand-drawn animation cel, comprising:

(a) a nonvolatile memory device;
and
(b) a plurality of machine instructions stored on the nonvolatile memory device, which when executed on the computer, effect a plurality of functions, including:
rendering a colored image, and while doing so, producing surface normal data for surfaces in the colored image;
(ii) when rendering the colored image, comparing a predetermined threshold angle with angles at which light rays intersect with the surfaces in different portions of the rendered image to determine which of a plurality of predefined colors are applied to the surfaces;
(iii) creating color lines in the colored image that delineate differently colored portions of the colored image by detecting edges between the differently colored portions along which the color lines are extended;
(iv) creating contour lines that follow an outline of an object in the colored image and which define any curves on any interior surfaces of the object by detecting edges in the colored image as a function of the surface normal data;
and
(v) compositing the colored image, the color lines, and the contour lines to produce the cel image, said color lines and contour lines simulating outlining in the cel image of a corresponding animation cel and said predefined colors applied to the different portions of the colored image simulating paint colors applied to the corresponding animation cel.

6 more elements

Dependencies are inferred from the claim text.

Simulating cel animation and shading

Life of this patent

Simulating cel animation and shading

Life of this patent

Abstract

Claims30