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glsl/smooth_heaviside.glsl

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+// A useful filter, behaves like a smoothly parameterized smooth Heaviside
+// function.
+// 
+// Inputs:
+//   x  input scalar (-inf, inf)
+//   t  control steepness of step function: --> 0 more linear, --> inf more like
+//     Heaviside function (piecewise constant function x<0--> -1 , x>0 --> 1)
+// Returns scalar value 
+float smooth_heaviside( float x, float t)
+{
+  return (1./(1.+exp(-2.*t*(x)))-1./2.)/(1./(1.+exp(-2.*t*1.))-1./2.);
+}
+