three.js/examples/jsm/shaders/CopyShader.js

/**
 * Full-screen textured quad shader
 */

var CopyShader = {

	uniforms: {

		'tDiffuse': { value: null },
		'opacity': { value: 1.0 }

	},

	vertexShader: [

		'varying vec2 vUv;',

		'void main() {',

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

		'}'

	].join( '\n' ),

	fragmentShader: [

		'uniform float opacity;',

		'uniform sampler2D tDiffuse;',

		'varying vec2 vUv;',

		'void main() {',

		'	vec4 texel = texture2D( tDiffuse, vUv );',
		'	gl_FragColor = opacity * texel;',

		'}'

	].join( '\n' )

};

export { CopyShader };