three.js/examples/js/shaders/PixelShader.js

( function () {

	/**
 * Pixelation shader
 */
	var PixelShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'resolution': {
				value: null
			},
			'pixelSize': {
				value: 1.
			}
		},
		vertexShader: [ 'varying highp vec2 vUv;', 'void main() {', 'vUv = uv;', 'gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );', '}' ].join( '\n' ),
		fragmentShader: [ 'uniform sampler2D tDiffuse;', 'uniform float pixelSize;', 'uniform vec2 resolution;', 'varying highp vec2 vUv;', 'void main(){', 'vec2 dxy = pixelSize / resolution;', 'vec2 coord = dxy * floor( vUv / dxy );', 'gl_FragColor = texture2D(tDiffuse, coord);', '}' ].join( '\n' )
	};

	THREE.PixelShader = PixelShader;

} )();