RSL
Color Ramps


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Introduction

This tutorial provides a couple of examples of shaders that apply a simple color ramp to a surface.


Simple Color Ramp

Using the mix() function a color can be assigned that changes smoothly in either the 's' or the 't' direction.



Figure 1

Listing 1

surface
ramp1(float  Kfb = 1;
     color   left = color(1,0,0),
             right = color(1,1,0))
{
color    surfcolor = mix(left, right, s);
  
Oi = Os;
Ci = Oi * Cs * surfcolor * Kfb;
}

Color Step

Using the smoothstep() function the color of a surface can be made to change more or less abruptly at a specific location.



Figure 2

Listing 2

surface ramp2(float   Kfb = 1,
                      blur = 0.1,
                      sdist = 0.5;
               color  left = color(1,0,0),
                      right = color(1,1,0))
{
color surfcolor = mix(left, right, smoothstep(sdist-blur,sdist+blur,s));
  
Oi = Os;
Ci = Oi * Cs * surfcolor * Kfb;
}


© 2002- Malcolm Kesson. All rights reserved.