35 lines
843 B
C++
35 lines
843 B
C++
#pragma once
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#include <cstdint>
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static inline float bellCurveApproximation(float x, float inverseWidth)
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{
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if (x < 0)
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x = -x;
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const auto nx = x * inverseWidth * 4;
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if (nx > 2)
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return 0.0f;
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const auto x2 = nx * nx;
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const auto x3 = x2 * nx;
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const auto res = 1.0f + 0.27606958941084f * x3 - 0.80213917882168f * x2;
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return res < 0.0f ? 0.0f : res;
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}
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// Function start at 0 (x=0) and goes smoothly up to 1 and arrives 1 at x=width
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// inverse width has to be 1 / width (should be cached outside)
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static inline float stepFunction(float x, float width, float inverseWidth)
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{
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if (x < 0.0f)
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return 0.0f;
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if (x >= width)
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return 1.0f;
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auto bellInvWidth = inverseWidth * 0.5f;
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auto nx = (-x + width) * bellInvWidth * 4;
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auto x2 = nx * nx;
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auto x3 = x2 * nx;
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return 1 + 0.2760695894 * x3 - 0.8021391 * x2;
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} |