[Gzz-commits] gzz/Documentation/Manuscripts/Paper paper.tex

[Janne V. Kujala]

CVSROOT:        /cvsroot/gzz
Module name:    gzz
Changes by:     Janne V. Kujala <address@hidden>        02/11/18 04:07:48

Modified files:
        Documentation/Manuscripts/Paper: paper.tex 

Log message:
        colors

CVSWeb URLs:
http://savannah.gnu.org/cgi-bin/viewcvs/gzz/gzz/Documentation/Manuscripts/Paper/paper.tex.diff?tr1=1.35&tr2=1.36&r1=text&r2=text

Patches:
Index: gzz/Documentation/Manuscripts/Paper/paper.tex
diff -u gzz/Documentation/Manuscripts/Paper/paper.tex:1.35 
gzz/Documentation/Manuscripts/Paper/paper.tex:1.36
--- gzz/Documentation/Manuscripts/Paper/paper.tex:1.35  Mon Nov 18 02:09:47 2002
+++ gzz/Documentation/Manuscripts/Paper/paper.tex       Mon Nov 18 04:07:48 2002
@@ -206,6 +206,55 @@
 but too many different colors in one texture are perceived just 
 as a mix of many colors, making all such textures look the same.
 
+Therefore, we use a small palette of carefully chosen colors for each texture,
+independent of the basis textures producing the shape of the final texture. 
+Register combiners are used to combine the shape with the colors 
+as explained in the following sections.
+
+The most important constraint for the colors is readability:
+black text must have good contrast with the texture.
+Additionally, the colors should be perceptually uniformly distributed
+and ``balanced'' to avoid overloading of color perception.
+
+Usually color perception is divided to lightness, hue, 
+and saturation (the chromatic purity), which are nonlinearly
+related to the usual RGB values.
+The are many nonlinear color spaces, such as CIE $L^*a^*b^*$ 
+\cite{cie86colorimetry}, 
+designed to represent the perceived components of color 
+on a uniform scale.
+
+To address readability, we only use colors with the CIE $L^*$
+lightness value over 80 (percent of maximum).
+However, because the texture shapes should also be visible, 
+we use one half dark colors and one half light colors in the 
+range to have some contrast for the shapes.
+Even though the register combiners interpolate linearly between 
+the colors in the palette, the lightness of an intermediate
+color is still between the two colors, because perceived
+lightness is a monotonous function of luminance.
+For correct computation of the color lightness, 
+it is essential that the display gamma is adjusted properly
+for linear RGB reproduction.
+
+To have balanced colors, we choose the hues from a distribution
+concentrated on one random hue with a random variance and
+saturations chosen from an ad hoc distribution.
+This produces related colors with high probability, but still
+allows flashy palettes to occur occasionally.
+
+Because the $a^*b^*$ plane of the CIE $L^*a^*b^*$ color space seems to 
+have too large angle of blue for light colors, 
+we actually choose the hues by 
+interpolating uniformly between seven primary colors,
+with orange added between the usual six colored corners of the RGB cube.
+
+Opposite color schemes could also be used for more variation, 
+but because the combiners can produce any color in the convex hull 
+of the palette, the interpolated colors would easily span too
+much area on the color circle.
+
+\if0
 - color contrast needed for recognizable shapes \\
 \\
 - RGB not perceptually uniform \\
@@ -225,7 +274,6 @@
 - color space similar to CIELAB
 - hues interpolated between 7 primaries
 - hue chosen from a distribution concentrated on one color with random 
variance \\
-- could also use opposite color schemes \\
 - saturation random using ad hoc distribution \\
 - readability: $L^* \ge 80$ \\
 - good contrast for shapes guaranteed by choosing dark and light colors 
@@ -236,6 +284,7 @@
 {\bf jvk}
 
 READABILITY - screen gamma
+\fi
 
 \subsection{Basis textures}
 
@@ -343,6 +392,8 @@
 
 Offset textures used for creating new shapes.
 
+XXX
+
 \section{Example application}
 
 \begin{figure*}
@@ -358,6 +409,9 @@
 
 \section{Software availability}
 
+An implementation of the unique textures is available as part of 
+the Gzz-prototype \url{http://gzz.info}.
+
 {\bf jvk}
 
 \section{Conclusions}
@@ -369,6 +423,8 @@
 Further work: NV30
 
 Textures with alpha/depth/lighting: irregular edges, holes, and bumps
+
+Objections: readability, interference with colored documents
 
 \section{MPEG Animation}
 [not to be included in final ms.]