:// ST Coloration

These images show the results of using the RenderMan Shading Language (RSL) to write a variety of special effects surface shaders. The notes and RSL code accompanying each image explain how each effect was achieved.

Cross

if (s > .3 && s < 0.7)
surfcolor = color(0.980,0.615,0.2);
else
surfcolor = color(0.219,0.219,0.219);
if (t > .3 && t < .7)
surfcolor = color(0.980,0.615,0.2);

Circle

if ((s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) > 0.1)
surfcolor = color(0.219,0.219,0.219);
else
surfcolor = color(0.980,0.615,0.2);

Diagonal

if((s + t >= 1))
surfcolor = color(0.219,0.219,0.219);
else
surfcolor = color(0.980,0.615,0.2);

Curve

if(( s*s + t*t < 1 ))
surfcolor = color(0.219,0.219,0.219);
else
surfcolor = color(0.980,0.615,0.2);

Target

I have a fondness for the British Target symbol. Creating this pattern gave me an understanding of layering patterns ontop of each other, in this case circles.

if ((s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.2)
surfcolor = color(0.007,0.176,0.623);
else
surfcolor = color(0.219,0.219,0.219);
if ((s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.1)
surfcolor = color(0.988,0.960,0.960);
if ((s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.0375)
surfcolor = color(0.815,0.086,0.086);

Custom Pattern

After creating the target I decided to play with layering a little more by overlaying curves ontop of the original pattern. I also had to use and statements to draw the portions of the circle that are diced up by the curves

if ((s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.2)
surfcolor = color(.980,0.615,0.2);
else
surfcolor = color(0.219,0.219,0.219);

if ((s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.1)
surfcolor = color(.219,0.219,0.219);

if ((s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.0375)
surfcolor = color(1.0,1.0,1.0);
if(( s*s + t*t > .5 ))
surfcolor = color(0.219,0.219,0.219);

if(( s*s + t*t > .6 ) && (s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.2)
surfcolor = color(.980,0.615,0.2);

if(( s*s + t*t > 1))
surfcolor = color(0.219,0.219,0.219);
if(( s*s + t*t > 1.1) && (s-0.5)*(s-0.5)+(t-0.5)*(t-0.5) < 0.2)
surfcolor = color(.980,0.615,0.2);