kc3-lang/angle/src/common/mathutil.cpp

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• Hash : 92b9cd57
  Author :
  Date : 2013-05-30T00:14:48
  

  Added support for the GL_RGB9_E5 format.
  
  git-svn-id: https://angleproject.googlecode.com/svn/branches/es3proto@2363 736b8ea6-26fd-11df-bfd4-992fa37f6226
  

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• src/common/mathutil.cpp

• #include "precompiled.h"
  //
  // Copyright (c) 2013 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  
  // mathutil.cpp: Math and bit manipulation functions.
  
  #include "common/mathutil.h"
  
  namespace gl
  {
  
  struct RGB9E5Data
  {
      unsigned int R : 9;
      unsigned int G : 9;
      unsigned int B : 9;
      unsigned int E : 5;
  };
  
  // B is the exponent bias (15)
  static const int g_sharedexp_bias = 15;
  
  // N is the number of mantissa bits per component (9)
  static const int g_sharedexp_mantissabits = 9;
  
  // Emax is the maximum allowed biased exponent value (31)
  static const int g_sharedexp_maxexponent = 31;
  
  static const float g_sharedexp_max = ((pow(2.0f, g_sharedexp_mantissabits) - 1) /
                                         pow(2.0f, g_sharedexp_mantissabits)) *
                                       pow(2.0f, g_sharedexp_maxexponent - g_sharedexp_bias);
  
  unsigned int convertRGBFloatsTo999E5(float red, float green, float blue)
  {
      const float red_c = std::max<float>(0, std::min(g_sharedexp_max, red));
      const float green_c = std::max<float>(0, std::min(g_sharedexp_max, green));
      const float blue_c = std::max<float>(0, std::min(g_sharedexp_max, blue));
  
      const float max_c = std::max<float>(std::max<float>(red_c, green_c), blue_c);
      const float exp_p = std::max<float>(-g_sharedexp_bias - 1, floor(log(max_c))) + 1 + g_sharedexp_bias;
      const int max_s = floor((max_c / (pow(2.0f, exp_p - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f);
      const int exp_s = (max_s < pow(2.0f, g_sharedexp_mantissabits)) ? exp_p : exp_p + 1;
  
      RGB9E5Data output;
      output.R = floor((red_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f);
      output.G = floor((green_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f);
      output.B = floor((blue_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f);
      output.E = exp_s;
  
      return *reinterpret_cast<unsigned int*>(&output);
  }
  
  void convert999E5toRGBFloats(unsigned int input, float *red, float *green, float *blue)
  {
      const RGB9E5Data *inputData = reinterpret_cast<const RGB9E5Data*>(&input);
  
      *red = inputData->R * pow(2.0f, (int)inputData->E - g_sharedexp_bias - g_sharedexp_mantissabits);
      *green = inputData->G * pow(2.0f, (int)inputData->E - g_sharedexp_bias - g_sharedexp_mantissabits);
      *blue = inputData->B * pow(2.0f, (int)inputData->E - g_sharedexp_bias - g_sharedexp_mantissabits);
  }
  
  }
  

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