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Fix R11G11B10 decode - it's a truncated half format

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* ie. not just an unnormalised mantissa plus biased exponent, it has proper
  IEEE style float properties with hidden bit on the mantissa etc. So full
  decoding is necessary, contrary to what some of the docs say :(.
This commit is contained in:
baldurk
2014-11-27 00:49:05 +00:00
parent 16dd0b77f4
commit d4bc4e2999
1 changed files with 58 additions and 9 deletions
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renderdoc/maths/formatpacking.h
+58 -9
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@@ -53,16 +53,65 @@ inline uint32_t ConvertToR10G10B10A2(Vec4f data)
inline Vec3f ConvertFromR11G11B10(uint32_t data)
{
uint32_t xMantissa = ((data>> 0) & 0x3f);
uint32_t xExponent = ((data>> 6) & 0x1f);
uint32_t yMantissa = ((data>>11) & 0x3f);
uint32_t yExponent = ((data>>17) & 0x1f);
uint32_t zMantissa = ((data>>22) & 0x1f);
uint32_t zExponent = ((data>>27) & 0x1f);
uint32_t mantissas[3] = {
(data>> 0) & 0x3f,
(data>>11) & 0x3f,
(data>>22) & 0x1f,
};
int32_t exponents[3] = {
(data>> 6) & 0x1f,
(data>>17) & 0x1f,
(data>>27) & 0x1f,
};
return Vec3f((float(xMantissa)/64.0f)*powf(2.0f, (float)xExponent - 15.0f),
(float(yMantissa)/32.0f)*powf(2.0f, (float)yExponent - 15.0f),
(float(zMantissa)/32.0f)*powf(2.0f, (float)zExponent - 15.0f));
Vec3f ret;
uint32_t *retu = (uint32_t *)&ret.x;
// floats have 23 bit mantissa, 8bit exponent
// R11G11B10 has 6/6/5 bit mantissas, 5bit exponents
const int mantissaShift[] = { 23-6, 23-6, 23-5 };
for(int i=0; i < 3; i++)
{
if(mantissas[i] == 0 && exponents[i] == 0)
{
retu[i] = 0;
}
else
{
if(exponents[i] == 0x1f)
{
// infinity or nan
retu[i] = 0x7f800000 | mantissas[i] << mantissaShift[i];
}
else if(exponents[i] != 0)
{
// shift exponent and mantissa to the right range for 32bit floats
retu[i] = (exponents[i] + (127-15)) << 23 | mantissas[i] << mantissaShift[i];
}
else if(exponents[i] == 0)
{
// we know xMantissa isn't 0 also, or it would have been caught above
exponents[i] = 1;
// shift until hidden bit is set
while((mantissas[i] & 0x40) == 0)
{
mantissas[i] <<= 1;
exponents[i]--;
}
// remove the hidden bit
mantissas[i] &= ~0x40;
retu[i] = (exponents[i] + (127-15)) << 23 | mantissas[i] << mantissaShift[i];
}
}
}
return ret;
}
/*