Step and interpolate.

gentype smoothstep ( gentype edge0,
  gentype edge1,
  gentype x)
gentype smoothstep ( float edge0,
  float edge1,
  gentype x)

gentype smoothstep (double edge0, double edge1, gentype x) // if double extension enabled
gentype smoothstep (half edge0, half edge1, gentype x) // if half extension enabled


Returns 0.0 if x less than or equal to edge0 and 1.0 if x greater than or equal to edge1 and performs smooth Hermite interpolation between 0 and 1 when edge0 < x < edge1. This is useful in cases where you would want a threshold function with a smooth transition.

This is equivalent to:

          gentype t;
          t = clamp(((x - edge0) /     (edge1 - edge0), 0, 1);
          return t * t * (3 - 2 * t );

Results are undefined if edge0 greater than or equal to edge1 or if x, edge0 or edge1 is a NaN.

This function can be implemented using contractions such as mad or fma.


Built-in common functions operate component-wise and the description is per-component. We use the generic type name gentype to indicate that the function can take float, float2, float4, float8, or float16 as the type for the arguments.

The built-in common functions are implemented using the round to nearest even rounding mode.

If extended with cl_khr_fp64, generic type name gentype may indicate double and double{2|4|8|16} as arguments and return values. If extended with cl_khr_fp16, generic type name gentype may indicate half and half{2|4|8|16} as arguments and return values.


OpenCL Specification

Also see

Common Functions

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