Shaders

colorramp - A six-color ramp shader

 
/* colorramp.sl shader - dsward@webnation.com 
This shader cycles through a table of colors to produce color shift effects:
colorScale - the scale, larger values increases the cycle length
colorOffset - vary this parameter to move the colors
    typically 0 to 1 for a full cycle
mapType - 0=x, 1=y, 2=z, 3=s, 4=t
shadingType = 0=constant, 1=constant, 2=plastic, 3=matte, 4=glow, 5=halo
color1-color6 - the sequence of colors to shift through
Ks, Kd, Ka, roughness, specularcolor - the usual meanings
*/
 
surface
colorramp (
       float colorScale = 1;
       float colorOffset = 0;
	   float mapType = 0;
	   float shadingType = 0;
	   color color1 = color(0, 0, 1);
	   color color2 = color(0, 1, 1);
	   color color3 = color(0, 1, 0);
	   color color4 = color(1, 1, 0);
	   color color5 = color(1, 0, 0);
	   color color6 = color(1, 0, 1);
 
	   color opacity1 = color(1, 1, 1);
	   color opacity2 = color(1, 1, 1);
	   color opacity3 = color(1, 1, 1);
	   color opacity4 = color(1, 1, 1);
	   color opacity5 = color(1, 1, 1);
	   color opacity6 = color(1, 1, 1);
	   
       float Ks = 0.5, Kd = 0.5, Ka=1, roughness= 0.1, attenuation = 2; 
	   color specularcolor=1;
   )
{
   float cmap;
   point PP;
   color interpColor;
   color interpOpacity;
   point Nf, V;
   point NN, II;
   float falloff;
 
  PP = transform ("shader", P);
  cmap =  xcomp(PP);
  if (mapType == 1) cmap =  ycomp(PP);
  if (mapType == 2) cmap =  zcomp(PP);
  if (mapType == 3) cmap =  s;
  if (mapType == 4) cmap =  t;
  
  cmap *= colorScale;
  cmap += colorOffset;
  cmap = mod(cmap, 1);
  
  interpColor = color spline (cmap, 
    color1, color1, color2, color3, color4, color5, color6, color1, color1);
 
  interpOpacity = color spline (cmap, 
    opacity1, opacity1, opacity2, opacity3, opacity4, opacity5, opacity6, opacity1, opacity1);
 
  if (shadingType == 0)
  {
  	/* constant */
  	Oi = interpOpacity;
  	Ci = interpColor * interpOpacity;
  }
 
  if (shadingType == 1)
  {
  	/* no show-through */
  	Oi = interpOpacity;
  	Ci = interpColor;
  }
 
  if (shadingType == 2)
  {
  	/* plastic shading */
    Nf = faceforward( normalize(N), I );
    V = -normalize(I);
    Ci = interpOpacity * ( interpColor * (Ka*ambient() + Kd*diffuse(Nf)) + 
	 	specularcolor * Ks * specular(Nf, V, roughness) );
  }
 
  if (shadingType == 3)
  {
	  /* matte shading */
	  Nf = faceforward(normalize(N),I);
	  Ci = interpOpacity * interpColor * ( Ka*ambient() + Kd * diffuse(Nf) ) ;
  }
 
  if (shadingType == 4)
  {
	  /* glow shading */
	  NN = normalize(N);
	  II = normalize(I);
	  falloff = II.NN;	/* Direct incidence has cosine closer to 1.*/
 
	  if (falloff < 0) 
	  {  		/* Back of sphere only */
		  /* Normalize falloff by lengths of I and N */
		  falloff = falloff * falloff / (II.II * NN.NN) ;
		  falloff = pow(falloff, attenuation);
		  Ci = interpColor * interpOpacity * falloff;
		  Oi = interpOpacity * falloff;
	  } 
	  else
	  {
		  Oi = 0;
	  }
  }
 
  if (shadingType == 5)
  {
	  /* halo shading */
	  NN = normalize(N);
	  II = normalize(I);
	  falloff = II.NN;	/* Direct incidence has cosine closer to 1.*/
 
	  if (falloff < 0) 
	  {  		/* Back of sphere only */
		  /* Normalize falloff by lengths of I and N */
		  falloff = falloff * falloff / (II.II * NN.NN) ;
		  falloff = 1 - falloff;
		  falloff = pow(falloff, attenuation);
		  Ci = interpColor * interpOpacity * falloff;
		  Oi = interpOpacity * falloff;
	  } 
	  else
	  {
		  Oi = 0;
	  }
  }
 
 
}