( function () {

	/**
 * Sepia tone shader
 * based on glfx.js sepia shader
 * https://github.com/evanw/glfx.js
 */
	const SepiaShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'amount': {
				value: 1.0
			}
		},
		vertexShader:
  /* glsl */
  `

		varying vec2 vUv;

		void main() {

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

		}`,
		fragmentShader:
  /* glsl */
  `

		uniform float amount;

		uniform sampler2D tDiffuse;

		varying vec2 vUv;

		void main() {

			vec4 color = texture2D( tDiffuse, vUv );
			vec3 c = color.rgb;

			color.r = dot( c, vec3( 1.0 - 0.607 * amount, 0.769 * amount, 0.189 * amount ) );
			color.g = dot( c, vec3( 0.349 * amount, 1.0 - 0.314 * amount, 0.168 * amount ) );
			color.b = dot( c, vec3( 0.272 * amount, 0.534 * amount, 1.0 - 0.869 * amount ) );

			gl_FragColor = vec4( min( vec3( 1.0 ), color.rgb ), color.a );

		}`
	};

	THREE.SepiaShader = SepiaShader;

} )();