Pixar

Pixar Animation Studios

Mitch Prater

Computer animators have, till now, largely relegated themselves to using point light sources when simulating directional light sources in computer graphics and animation. The illumination achieved is computationally feasible but not totally realistic. While it is possible to use a finite light source of given size and shape to achieve a more realistic effect, the radiosity analysis required to calculate the illumination effect of such a light source is so cumbersome that it cannot be used for real-time computer animation. The described invention allows the animator to approximate the illumination effect of a finite light source by using a point source of varying location and intensity. Another embodiment of the invention allows the animator to realistically simulate ambient light by a similar method. The resulting illumination effects are comparable to those achieved with full radiosity analyses at much lower computational loads.

Pseudo area lights

A method for manipulating color values in a computer graphics system. Colors are mapped into a color space referred to as 'HSY space,' which provides independent control over the orthogonal parameters of hue, saturation and luminance. The intuitive color description qualities of hue and saturation are retained in combination with the luminance parameter, which is specifically tuned to the response of the human eye and a specific display system. The present invention thus provides ease of use for the graphic artist without the hue and saturation dependent luminance response of prior art methods. Color image data in HSY format is manipulated by a color graphics editing or rendering process by altering hue, saturation and luminance individually. The graphic artist is thus able to select the appropriate color by using tints, shades and tones. In one embodiment, HSY color data is converted into a second color data format, such as RGB, for display or storage purposes to meet the physical requirements of display devices. A reverse transformation is used to convert scanned image data in RGB format into HSY data for manipulation in HSY space by the editing process. In addition, two hue preserving transformations are described which map the unit HSY color space into the unit RGB color space.

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Kentfield, CA, United States of America

Mitch Prater