mudbox::half_ Class Reference

#include <image.h>

List of all members.

Detailed Description

Half precision (16 bit) float class. Supports fast conversion between float and half precision.

Format is compatible with openEXRs half precision type. 1 sign bit, 5 exponent bits (bias = 15), 10 fraction bits.


Public Member Functions
  half_ ()
  half_ (float f)
  operator float () const
half_ &  operator= (float f)

Constructor & Destructor Documentation

mudbox::half_::half_ (   )  [inline]
  
00041 {};
mudbox::half_::half_ (  float  f  )  [inline]
  
00043     {
00044         unsigned int   x    = *(unsigned int *)&f;
00045         unsigned int   frac = (x >> 13) & 0x03ff;
00046         int            exp  = (int)((x >> 23) & 0xff) - 127;
00047 
00048         m_bits = (x >> 16) & 0x8000;  // extract the sign bit
00049 
00050         if (exp > 16) {      // handle overflows/underflows
00051             exp  = 16;
00052             frac = 0x03ff;
00053         } else if (exp <= -15) {
00054             frac = 0;
00055             exp  = -15;
00056         }
00057 
00058         m_bits |= ((exp + 15) << 10) | frac;
00059     }

Member Function Documentation

mudbox::half_::operator float (   )  const [inline]
  
00065     {
00066         int           exp  = (m_bits >> 10) & 0x1f;
00067         unsigned int  f    = (m_bits & 0x8000) << 16; // extract the sign bit
00068         unsigned int  frac = (m_bits & 0x03ff) << 13;
00069 
00070         if (exp == 0x1f) {      // convert 16-bit FP inf/NaN to 32-bit inf/NaN value
00071             exp =  0xff - ExponentBiasDelta;
00072         } else if (exp == 0) {
00073             exp = -ExponentBiasDelta;  // convert 16-bit FP zero/denorm to 32-bit zero/denorm value
00074         }
00075 
00076         f |= ((exp + ExponentBiasDelta) << 23) | frac;
00077         return *(float *)&f;
00078     }
half_& mudbox::half_::operator= (  float  f  )  [inline]
  
00081     {
00082         *this = half_ (f);
00083         return *this;
00084     }
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