LYGIA Shader Library

Use:

<vec4> pack(<float> v)

Check it on Github

#ifndef CONST_PACKING
#define CONST_PACKING
const float PackUpscale = 256. / 255.; // fraction -> 0..1 (including 1)
const float UnpackDownscale = 255. / 256.; // 0..1 -> fraction (excluding 1)
const vec3 PackFactors = vec3( 256. * 256. * 256., 256. * 256.,  256. );
const vec4 UnpackFactors = UnpackDownscale / vec4( PackFactors, 1. );
const float ShiftRight8 = 1. / 256.;
#endif

#ifndef FNC_PACK
#define FNC_PACK

vec4 pack( const in float v ) {
    vec4 r = vec4( fract( v * PackFactors ), v );
    r.yzw -= r.xyz * ShiftRight8; // tidy overflow
    return r * PackUpscale;
}

#endif