GLSL depth texture and GLSL

// VERTEXuniform vec3 CamPos, CamDir;uniform float DepthNear, DepthFar;varying float CameraDepth;...    vec3 offset = (gl_Vertex.xyz / gl_Vertex.w) - CamPos;    float z = -dot(offset, CamDir);    CameraDepth = (z - DepthNear) / (DepthFar - DepthNear);...// FRAGMENTvarying float CameraDepth;...    gl_FragColor.xyz = vec3(CameraDepth);    // Or whatever you want exactly here...    gl_FragColor.w = 1.0;...

/// Packing a [0-1] float value into a 4D vector where each component will be a 8-bits integervec4 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 integerfloat 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));}