three.js/examples/js/shaders/DotScreenShader.js

/**
 * Dot screen shader
 * based on glfx.js sepia shader
 * https://github.com/evanw/glfx.js
 */

THREE.DotScreenShader = {

	uniforms: {

		'tDiffuse': { value: null },
		'tSize': { value: new THREE.Vector2( 256, 256 ) },
		'center': { value: new THREE.Vector2( 0.5, 0.5 ) },
		'angle': { value: 1.57 },
		'scale': { value: 1.0 }

	},

	vertexShader: [

		'varying vec2 vUv;',

		'void main() {',

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

		'}'

	].join( '\n' ),

	fragmentShader: [

		'uniform vec2 center;',
		'uniform float angle;',
		'uniform float scale;',
		'uniform vec2 tSize;',

		'uniform sampler2D tDiffuse;',

		'varying vec2 vUv;',

		'float pattern() {',

		'	float s = sin( angle ), c = cos( angle );',

		'	vec2 tex = vUv * tSize - center;',
		'	vec2 point = vec2( c * tex.x - s * tex.y, s * tex.x + c * tex.y ) * scale;',

		'	return ( sin( point.x ) * sin( point.y ) ) * 4.0;',

		'}',

		'void main() {',

		'	vec4 color = texture2D( tDiffuse, vUv );',

		'	float average = ( color.r + color.g + color.b ) / 3.0;',

		'	gl_FragColor = vec4( vec3( average * 10.0 - 5.0 + pattern() ), color.a );',

		'}'

	].join( '\n' )

};