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Economical Highlights and Sparkles For Three Dimensional Shaded Pictures

IP.com Disclosure Number: IPCOM000048699D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Appel, A: AUTHOR [+3]

Abstract

Low-cost computer graphic techniques for generating a shaded picture of solid objects are described. Highlights, lowlights and sparkles, which do not require extensive CPU time or memory are utilized to greatly improve human perception of computer-generated shaded pictures of solid objects.

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Economical Highlights and Sparkles For Three Dimensional Shaded Pictures

Low-cost computer graphic techniques for generating a shaded picture of solid objects are described. Highlights, lowlights and sparkles, which do not require extensive CPU time or memory are utilized to greatly improve human perception of computer-generated shaded pictures of solid objects.

Referring to Fig. 1, highlights 2.4 are defined wherein a local brightness on a shaded picture of a solid 3 which is taken to be a line 2 or several lines 4. A sparkle 6 is defined as a local bright spot usually on the corner of a solid 3. Highlights 2,4 or sparkles 6 of a solid object usually occur in nature because the solid object is usually not a perfect geometric shape or because solid objects are usually made with chamfers, rounds, or some other imperfection which allows local incident or reflective highlight values (Fig. 2).

If planes A and B are facing toward a light source S, some part of the round 8 is better illuminated then A or B, hence, the intersection edge of AB should be drawn brighter than A or B. If A is in a shadow and B is illuminated, some visible part of the round 8 should be in the shadow, even if A is invisible. Even if A is not in the shadow, but is less illuminated than B, some part of the round 8 should be darker than B. In this case the round 8 creates a lowlight. Highlights, sparkles and lowlights can be used inexpensively to make pictures more vivid, and can be used to prevent a surface from fading into the background when drawing shaded pictures.

Referring to Fig. 3A, assume the light is at eye level to avoid shadows. All surfaces of the base 10 and cube 12 thereon could be of the same color.

The cube 12 may not stand out against the base 10 to s degree that a computer-generated picture of the composite solid objects may appear as a monotone structure, as in Fig. 3B. Even if the intensity varies with depth, the cube 12 may not be well defined. However, with highlights 14, sparkles 16 and lowlights 18, human perception of the computer-improved.

The mechanism of the eye tends to accentuate differences in illumination so drawing highlights and lowlights with slender lines (1 raster wide) is a reasonable approximation. Rounds can be assumed, not necessarily modeled, and sparkles can be drawn as larger bright dots or as stars depending upon taste or the application. Highlighted lines, lowlighted lines and sparkled corners could be sufficiently effective that accurate surface shading may not be necessary. Hence, these techniques would be very effective on conventional area fill color CRT display terminals. The key decisions to be made by a computer program are: A is a line edge, a highlight or a lowlight.

B is a corner point o...