three.js/examples/js/shaders/DepthRGBAUnpackedShader.js

/**
 * @author Ben Houston / bhouston / http://clara.io
 *
 * Test depth pack, unpack and range
 *
 */

THREE.DepthRGBAUnpackedShader = {

	vertexShader: THREE.ShaderChunk[ 'depth_vert' ],

	fragmentShader: [
    "#include <common>",
    "#include <packing>",
    "#include <logdepthbuf_pars_fragment>",

    "void main() {",

      "#include <logdepthbuf_fragment>",

      "#ifdef USE_LOGDEPTHBUF_EXT",

    		"float depth = gl_FragDepthEXT;",

    	"#else",

    		"float depth = gl_FragCoord.z;",

      "#endif",

    	 "gl_FragColor = vec4( vec3( unpackRGBAToLinearUnit( packLinearUnitToRGBA( depth ) ) ), 1.0 );",

      "}" ].join( "\n" )

};