three.js/examples/js/shaders/VerticalBlurShader.js

console.warn( "THREE.VerticalBlurShader: As part of the transition to ES6 Modules, the files in 'examples/js' were deprecated in May 2020 (r117) and will be deleted in December 2020 (r124). You can find more information about developing using ES6 Modules in https://threejs.org/docs/#manual/en/introduction/Installation." );
/**
 * Two pass Gaussian blur filter (horizontal and vertical blur shaders)
 * - described in http://www.gamerendering.com/2008/10/11/gaussian-blur-filter-shader/
 *   and used in http://www.cake23.de/traveling-wavefronts-lit-up.html
 *
 * - 9 samples per pass
 * - standard deviation 2.7
 * - "h" and "v" parameters should be set to "1 / width" and "1 / height"
 */

THREE.VerticalBlurShader = {

	uniforms: {

		"tDiffuse": { value: null },
		"v": { value: 1.0 / 512.0 }

	},

	vertexShader: [

		"varying vec2 vUv;",

		"void main() {",

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

		"}"

	].join( "\n" ),

	fragmentShader: [

		"uniform sampler2D tDiffuse;",
		"uniform float v;",

		"varying vec2 vUv;",

		"void main() {",

		"	vec4 sum = vec4( 0.0 );",

		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y - 4.0 * v ) ) * 0.051;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y - 3.0 * v ) ) * 0.0918;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y - 2.0 * v ) ) * 0.12245;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y - 1.0 * v ) ) * 0.1531;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y ) ) * 0.1633;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y + 1.0 * v ) ) * 0.1531;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y + 2.0 * v ) ) * 0.12245;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y + 3.0 * v ) ) * 0.0918;",
		"	sum += texture2D( tDiffuse, vec2( vUv.x, vUv.y + 4.0 * v ) ) * 0.051;",

		"	gl_FragColor = sum;",

		"}"

	].join( "\n" )

};