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

/**
 * Unpack RGBA depth shader
 * - show RGBA encoded depth as monochrome color
 */

THREE.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" )

};