basic: added a color spinner; utilities: added translations of inigo quilez' functions; weird: added psychedelic stars

utilities/inigo.glsl

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+// Translation (from C) of utility functions Inigo Quilez
+// explains in http://www.iquilezles.org/www/articles/functions/functions.htm
+float almostIdentity(float x, float m, float n) {
+    if(x > m) return x;
+
+    float a = 2.*n - m;
+    float b = 2.0*m - 3.0*n;
+    float t = x/m;
+
+    return (a*t + b)*t*t + n;
+}
+
+float impulse(float k, float x) {
+    float h = k * x;
+    return h*exp(1.0-h);
+}
+
+float cubic_pulse(float c, float w, float x) {
+    x = abs(x - c);
+    if(x > w) return .0;
+    x /= w;
+    return 1.0 - x*x*(3.0-2.0*x);
+}
+
+float parabola(float x, float k) {
+    return pow(4.0*x*(1.0-x), k);
+}