float16 (and more so float32) have many odd values
half the values are negative, many are larger than "1.0"
and many values are very close to 0.
Storing the 16bits as is, looses compression because of the mixture
of dense and sparse regions and also many completely unused ones.
This simply remaps
float16 is a sign bit followed by "positive is larger" exponent and mantisse
that way the up direction changes between negative and positive numbers
flipping the exponent and mantisse for positive numbers gives a compression
gain of 0.5% for both RCT and noRCT modes using the
ACES_OT_VWG_SampleFram
