minrt/MathETC1.hpp at master · wheresthecode/minrt · GitHub

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// https://bitbucket.org/wolfpld/etcpak
// Bartosz Taudul <wolf.pld@gmail.com>

#ifndef __DARKRL__MATH_HPP__
#define __DARKRL__MATH_HPP__

#include <algorithm>
#include <cmath>

template<typename T>
inline T AlignPOT(T val)
{
  if (val == 0) return 1;
  val--;
  for (unsigned int i = 1; i < sizeof(T) * 8; i <<= 1)
  {
    val |= val >> i;
  }
  return val + 1;
}

inline int CountSetBits(unsigned int val)
{
  val -= (val >> 1) & 0x55555555;
  val = ((val >> 2) & 0x33333333) + (val & 0x33333333);
  val = ((val >> 4) + val) & 0x0f0f0f0f;
  val += val >> 8;
  val += val >> 16;
  return val & 0x0000003f;
}

inline int CountLeadingZeros(unsigned int val)
{
  val |= val >> 1;
  val |= val >> 2;
  val |= val >> 4;
  val |= val >> 8;
  val |= val >> 16;
  return 32 - CountSetBits(val);
}

inline float sRGB2linear(float v)
{
  const float a = 0.055f;
  if (v <= 0.04045f)
  {
    return v / 12.92f;
  }
  else
  {
    return pow((v + a) / (1 + a), 2.4f);
  }
}

inline float linear2sRGB(float v)
{
  const float a = 0.055f;
  if (v <= 0.0031308f)
  {
    return 12.92f * v;
  }
  else
  {
    return (1 + a) * pow(v, 1 / 2.4f) - a;
  }
}

template<class T>
inline T SmoothStep(T x)
{
  return x*x*(3 - 2 * x);
}

inline unsigned char clampu8(int val)
{
  return std::min(std::max(0, val), 255);
}

template<class T>
inline T sq(T val)
{
  return val * val;
}

static inline int mul8bit(int a, int b)
{
  int t = a*b + 128;
  return (t + (t >> 8)) >> 8;
}

#endif