three.js/examples/js/shaders/LuminosityHighPassShader.js

( function () {

	/**
 * Luminosity
 * http://en.wikipedia.org/wiki/Luminosity
 */

	const LuminosityHighPassShader = {
		shaderID: 'luminosityHighPass',
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'luminosityThreshold': {
				value: 1.0
			},
			'smoothWidth': {
				value: 1.0
			},
			'defaultColor': {
				value: new THREE.Color( 0x000000 )
			},
			'defaultOpacity': {
				value: 0.0
			}
		},
		vertexShader: /* glsl */`

		varying vec2 vUv;

		void main() {

			vUv = uv;

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

		}`,
		fragmentShader: /* glsl */`

		uniform sampler2D tDiffuse;
		uniform vec3 defaultColor;
		uniform float defaultOpacity;
		uniform float luminosityThreshold;
		uniform float smoothWidth;

		varying vec2 vUv;

		void main() {

			vec4 texel = texture2D( tDiffuse, vUv );

			vec3 luma = vec3( 0.299, 0.587, 0.114 );

			float v = dot( texel.xyz, luma );

			vec4 outputColor = vec4( defaultColor.rgb, defaultOpacity );

			float alpha = smoothstep( luminosityThreshold, luminosityThreshold + smoothWidth, v );

			gl_FragColor = mix( outputColor, texel, alpha );

		}`
	};

	THREE.LuminosityHighPassShader = LuminosityHighPassShader;

} )();