Basic shader test 
n = normalize(N);
nf = faceforward(n, I);
float noiseBase = base + (noise(s)0.5);
float b = smoothstep(noiseBase, noiseBase + blend, t);
float dot = 1 nf.normalize(I);
Oi = mix(baseOpacity, topOpacity, b) * smoothstep(1  rimwidth, 1.0, dot);
surfcolor = mix(baseColor, topColor, b);
diffusecolor = Kd * diffuse(nf);
Ci = Oi * Cs * surfcolor * diffusecolor;
