utils: added exponential shaping functions from flong

utilities/flong.glsl

@@ -92,3 +92,47 @@ float quad_through_point(float x, vec2 ab) {
 
   return y;
 }
+
+// exponential shaping
+
+float exp_easing(float x, float a) {
+  float e = 0.00001;
+  a = clamp(a, 0.+e, 1.-e);
+
+  if (a < 0.5) {
+    a = 2.0*(a);
+    return pow(x, a);
+  }
+  a = 2.*(a-.5);
+  return pow(x, 1./(1.-a));
+}
+
+float double_exp_seat(float x, float a) {
+  float e = 0.00001;
+  a = clamp(a, .0+e, 1.-e);
+
+  if (x<=0.5) {
+    return pow(2.*x, 1.-a)/2.0;
+  }
+  return 1. - pow(2.*(1.-x), 1.-a)/2.;
+}
+
+float double_exp_sigmoid(float x, float a) {
+  float e = 0.00001;
+  a = 1.-clamp(a, .0+e, 1.-e);
+
+  if (x<=0.5){
+    return pow(2.0*x, 1.0/a)/2.0;
+  }
+  return 1.0 - (pow(2.0*(1.0-x), 1.0/a))/2.0;
+}
+
+float normalized_log_sigmoid(float x, float a) {
+  float e = 0.0001;
+  a = 1./(1.-clamp(a, 0.+e, 1.-e)) - 1.;
+
+  float b = 1.0 / (1.0 + exp(a));
+  float c = 1.0 / (1.0 + exp(0.-a));
+  a = 1. / (1. + exp(0. -((x-.5)*a*2.)));
+  return (a-b)/(c-b);
+}