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About the CoverAbout the Cover
About the CoverAbout the Cover
About the Cover
The cover image is the second in the “Gems” theme that I began last year. Andrew
Glassner and I bounced some ideas back and forth, and the design solidified pretty
quickly. The gems themselves are the same as in last year’s image.The picture was
generated at Pacific Data Images using their in-house software. All of the textures and
models are procedurally generated. The sand texture, the sand surface shape, the
woodgrain, the sea foam, and the starfish texture are all derived from fractal noise
patterns. I spent most of my time on the water, making it look all shiny and wet and
transparent, but not too transparent. The foam on the water’s surface was also very time-
consuming. Another challenge was to get the gems to all pile on top of each other
convincingly. I wrote a program that dropped them, one at a time, and as they fell, they
were rotated to the angle that moved them the furthest down without intersecting
anything that was there already. This program took a couple of hours to run, but it was
much faster than trying to place them by hand. The picture was rendered with a ray-
tracing program and took 50 hours on an Silicon Graphics 4D25 computer at a resolution
of 2250 × 3000 pixels with four samples per pixel.
Thaddeus Beier
Silicon Graphics Computer Systems
When Andrew asked if I wanted to do the cover for Graphics Gems II, I said “Sure . .
. we can reuse the software we built last year for Graphics Gems.” While it wasn’t quite
that simple, it was much easier to produce this cover than the first one. As before, the
image was designed on a color monitor producing red, green and blue pixels. For
printing, we needed to convert these pixels to cyan, magenta, yellow, and black pixels
(printer color space). Once in this form, the image was processed commercially to
produce half-toned film suitable for printing. This final step was performed at Kedie-
Orent, Sunnyvale, California, on their Crosfield digital prepress system.
As was the case with the first “Gems” picture, many of the original image colors could
not be exactly reproduced in print form. The colors had to be modified to map into the
set of colors that can be produced by the printer, its gamut. The trick is to do the
modification while maintaining the appearance of the image. In this picture, the colors
in the sand, shells, and water were mostly inside the printer gamut. However, some of
the gem colors, particularly the bright blue-greens, were far outside the gamut. The
transformation we applied was similar to the one we designed for Graphics Gems; colors
outside of the gamut were desaturated to colors of the same lightness while maintaining
the same hue. If one color of a particular hue needed to be desaturated, all colors of
the same hue would be desaturated to preserve shading detail. However, colors outside
of the gamut move more than colors inside of the gamut to maintain the overall
saturation.
The colors of the Graphics Gems II cover are lighter and more delicate than the cover
of Graphics Gems, and much more of the image lies in the interior of the printer gamut.
We tuned the transformation for this image to minimize the change to the less saturated
colors, preserving the subtle shading in the sand and water.
Thanks to Bill Wallace, who wrote the original gamut mapping software for Graphics
Gems, and to Ken Fishkin, who helped with the production of the cover this year.
Maureen Stone
Xerox Palo Alto Research Center
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