three.js/examples/js/shaders/UnpackDepthRGBAShader.js

( function () {

	/**
 * Unpack RGBA depth shader
 * - show RGBA encoded depth as monochrome color
 */
	var UnpackDepthRGBAShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'opacity': {
				value: 1.0
			}
		},
		vertexShader: [ 'varying vec2 vUv;', 'void main() {', '	vUv = uv;', '	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );', '}' ].join( '\n' ),
		fragmentShader: [ 'uniform float opacity;', 'uniform sampler2D tDiffuse;', 'varying vec2 vUv;', '#include <packing>', 'void main() {', '	float depth = 1.0 - unpackRGBAToDepth( texture2D( tDiffuse, vUv ) );', '	gl_FragColor = vec4( vec3( depth ), opacity );', '}' ].join( '\n' )
	};

	THREE.UnpackDepthRGBAShader = UnpackDepthRGBAShader;

} )();