three.js/examples/js/shaders/ToneMapShader.js

/**
 * @author miibond
 *
 * Full-screen tone-mapping shader based on http://www.cis.rit.edu/people/faculty/ferwerda/publications/sig02_paper.pdf
 */

THREE.ToneMapShader = {

	uniforms: {

		"tDiffuse": { value: null },
		"averageLuminance":  { value: 1.0 },
		"luminanceMap":  { value: null },
		"maxLuminance":  { value: 16.0 },
		"minLuminance":  { value: 0.01 },
		"middleGrey":  { value: 0.6 }
	},

	vertexShader: [

		"varying vec2 vUv;",

		"void main() {",

			"vUv = uv;",
			"gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );",

		"}"

	].join( "\n" ),

	fragmentShader: [

		"#include <common>",

		"uniform sampler2D tDiffuse;",

		"varying vec2 vUv;",

		"uniform float middleGrey;",
		"uniform float minLuminance;",
		"uniform float maxLuminance;",
		"#ifdef ADAPTED_LUMINANCE",
			"uniform sampler2D luminanceMap;",
		"#else",
			"uniform float averageLuminance;",
		"#endif",

		"vec3 ToneMap( vec3 vColor ) {",
			"#ifdef ADAPTED_LUMINANCE",
				// Get the calculated average luminance
				"float fLumAvg = texture2D(luminanceMap, vec2(0.5, 0.5)).r;",
			"#else",
				"float fLumAvg = averageLuminance;",
			"#endif",

			// Calculate the luminance of the current pixel
			"float fLumPixel = linearToRelativeLuminance( vColor );",

			// Apply the modified operator (Eq. 4)
			"float fLumScaled = (fLumPixel * middleGrey) / max( minLuminance, fLumAvg );",

			"float fLumCompressed = (fLumScaled * (1.0 + (fLumScaled / (maxLuminance * maxLuminance)))) / (1.0 + fLumScaled);",
			"return fLumCompressed * vColor;",
		"}",

		"void main() {",

			"vec4 texel = texture2D( tDiffuse, vUv );",

			"gl_FragColor = vec4( ToneMap( texel.xyz ), texel.w );",

		"}"

	].join( "\n" )

};