inline float4 EncodeFloatRGBA( float v ) {
  return frac( float4(1.0, 256.0, 65536.0, 16777216.0) * v );
}
inline float DecodeFloatRGBA( float4 rgba ) {
  return dot( rgba, float4(1.0, 1.0/256.0, 1.0/65536.0, 1.0/16777216.0) );
}