GLSL float to RGBA8 encoder

Packing a [0-1] float value into a 4D vector where each component will be a 8-bits integer:

vec4 packFloatToVec4i(const float value)
  const vec4 bitSh = vec4(256.0*256.0*256.0, 256.0*256.0, 256.0, 1.0);
  const vec4 bitMsk = vec4(0.0, 1.0/256.0, 1.0/256.0, 1.0/256.0);
  vec4 res = fract(value * bitSh);
  res -= res.xxyz * bitMsk;
  return res;

Unpacking a [0-1] float value from a 4D vector where each component was a 8-bits integer:

float unpackFloatFromVec4i(const vec4 value)
  const vec4 bitSh = vec4(1.0/(256.0*256.0*256.0), 1.0/(256.0*256.0), 1.0/256.0, 1.0);
  return(dot(value, bitSh));

Source of these codes: Gamedev forums

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