Reverse swipe

espmusicmouse/lib/ledtl/helpers/BellCurve.h

@@ -16,4 +16,20 @@ static inline float bellCurveApproximation(float x, float inverseWidth)
   const auto res = 1.0f + 0.27606958941084f * x3 - 0.80213917882168f * x2;
 
   return res < 0.0f ? 0.0f : res;
+}
+
+// Function start at 0 (x=0) and goes smoothly up to 1 and arrives 1 at x=width
+// inverse width has to be 1 / width (should be cached outside)
+static inline float stepFunction(float x, float width, float inverseWidth)
+{
+  if (x < 0.0f)
+    return 0.0f;
+  if (x >= width)
+    return 1.0f;
+
+  auto bellInvWidth = inverseWidth * 0.5f;
+  auto nx = (-x + width) * bellInvWidth * 4;
+  auto x2 = nx * nx;
+  auto x3 = x2 * nx;
+  return 1 + 0.2760695894 * x3 - 0.8021391 * x2;
 }