three.js/examples/js/postprocessing/ManualMSAARenderPass.js

/**
*
* Manual Multi-Sample Anti-Aliasing Render Pass
*
* @author bhouston / http://clara.io/
*
* This manual approach to MSAA re-renders the scene ones for each sample with camera jitter and accumulates the results.
*
* References: https://en.wikipedia.org/wiki/Multisample_anti-aliasing
*
*/

THREE.ManualMSAARenderPass = function ( scene, camera, params ) {

	THREE.Pass.call( this );

	this.scene = scene;
	this.camera = camera;

	this.sampleLevel = 4; // specified as n, where the number of samples is 2^n, so sampleLevel = 4, is 2^4 samples, 16.

	this.params = params || { minFilter: THREE.NearestFilter, magFilter: THREE.NearestFilter, format: THREE.RGBAFormat };
	this.params.minFilter = THREE.NearestFilter;
	this.params.maxFilter = THREE.NearestFilter;

	if ( THREE.CompositeShader === undefined ) {

		console.error( "THREE.ManualMSAARenderPass relies on THREE.CompositeShader" );

	}

	var compositeShader = THREE.CompositeShader;
	this.compositeUniforms = THREE.UniformsUtils.clone( compositeShader.uniforms );

	this.materialComposite = new THREE.ShaderMaterial(	{

		uniforms: this.compositeUniforms,
		vertexShader: compositeShader.vertexShader,
		fragmentShader: compositeShader.fragmentShader,
		premultipliedAlpha: true,
		transparent: true,
		blending: THREE.AdditiveBlending,
		depthTest: false,
		depthWrite: false

	} );

	this.camera2 = new THREE.OrthographicCamera( - 1, 1, 1, - 1, 0, 1 );
	this.scene2	= new THREE.Scene();
	this.quad2 = new THREE.Mesh( new THREE.PlaneGeometry( 2, 2 ), this.materialComposite );
	this.scene2.add( this.quad2 );

};

THREE.ManualMSAARenderPass.prototype = Object.create( THREE.Pass.prototype );

THREE.ManualMSAARenderPass.prototype = {

	constructor: THREE.ManualMSAARenderPass,

	dispose: function() {

		if ( this.sampleRenderTarget ) {

			this.sampleRenderTarget.dispose();
			this.sampleRenderTarget = null;

		}

	},


	setSize: function ( width, height ) {

		if ( this.sampleRenderTarget ) { this.sampleRenderTarget.setSize( width, height ); }

	},

	render: function ( renderer, writeBuffer, readBuffer, delta, maskActive ) {

		var camera = ( this.camera || this.scene.camera );
		var jitterOffsets = THREE.ManualMSAARenderPass.JitterVectors[ Math.max( 0, Math.min( this.sampleLevel, 5 ) ) ];

		if ( ! this.sampleRenderTarget ) {

			this.sampleRenderTarget = new THREE.WebGLRenderTarget( readBuffer.width, readBuffer.height, this.params );

		}

		var autoClear = renderer.autoClear;
		renderer.autoClear = false;

		this.compositeUniforms[ "scale" ].value = 1.0 / jitterOffsets.length;
		this.compositeUniforms[ "tForeground" ].value = this.sampleRenderTarget.texture;

		// render the scene multiple times, each slightly jitter offset from the last and accumulate the results.
		for ( var i = 0; i < jitterOffsets.length; i ++ ) {

			// only jitters perspective cameras.	TODO: add support for jittering orthogonal cameras
			var jitterOffset = jitterOffsets[i];
			if ( camera.setViewOffset ) {
				camera.setViewOffset( readBuffer.width, readBuffer.height,
					jitterOffset[ 0 ] * 0.0625, jitterOffset[ 1 ] * 0.0625,   // 0.0625 = 1 / 16
					readBuffer.width, readBuffer.height );
			}

			renderer.render( this.scene, camera, this.sampleRenderTarget, true );
			renderer.render( this.scene2, this.camera2, writeBuffer, (i === 0) );

		}

		// reset jitter to nothing.	TODO: add support for orthogonal cameras
		if ( camera.setViewOffset ) camera.setViewOffset( undefined, undefined, undefined, undefined, undefined, undefined );

		renderer.autoClear = autoClear;

	}

};

// These jitter vectors are specified in integers because it is easier.
// I am assuming a [-8,8) integer grid, but it needs to be mapped onto [-0.5,0.5)
// before being used, thus these integers need to be scaled by 1/16.
//
// Sample patterns reference: https://msdn.microsoft.com/en-us/library/windows/desktop/ff476218%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396
THREE.ManualMSAARenderPass.JitterVectors = [
	[
		[ 0, 0 ]
	],
	[
		[ 4, 4 ], [ - 4, - 4 ]
	],
	[
		[ - 2, - 6 ], [ 6, - 2 ], [ - 6, 2 ], [ 2, 6 ]
	],
	[
		[ 1, - 3 ], [ - 1, 3 ], [ 5, 1 ], [ - 3, - 5 ],
		[ - 5, 5 ], [ - 7, - 1 ], [ 3, 7 ], [ 7, - 7 ]
	],
	[
		[ 1, 1 ], [ - 1, - 3 ], [ - 3, 2 ], [ 4, - 1 ],
		[ - 5, - 2 ], [ 2, 5 ], [ 5, 3 ], [ 3, - 5 ],
		[ - 2, 6 ], [ 0, - 7 ], [ - 4, - 6 ], [ - 6, 4 ],
		[ - 8, 0 ], [ 7, - 4 ], [ 6, 7 ], [ - 7, - 8 ]
	],
	[
		[ - 4, - 7 ], [ - 7, - 5 ], [ - 3, - 5 ], [ - 5, - 4 ],
		[ - 1, - 4 ], [ - 2, - 2 ], [ - 6, - 1 ], [ - 4, 0 ],
		[ - 7, 1 ], [ - 1, 2 ], [ - 6, 3 ], [ - 3, 3 ],
		[ - 7, 6 ], [ - 3, 6 ], [ - 5, 7 ], [ - 1, 7 ],
		[ 5, - 7 ], [ 1, - 6 ], [ 6, - 5 ], [ 4, - 4 ],
		[ 2, - 3 ], [ 7, - 2 ], [ 1, - 1 ], [ 4, - 1 ],
		[ 2, 1 ], [ 6, 2 ], [ 0, 4 ], [ 4, 4 ],
		[ 2, 5 ], [ 7, 5 ], [ 5, 6 ], [ 3, 7 ]
	]
];