three.js/examples/js/wip/benchmark/PlaneBufferGeometry.js

/**
 * @author mrdoob / http://mrdoob.com/
 * based on http://papervision3d.googlecode.com/svn/trunk/as3/trunk/src/org/papervision3d/objects/primitives/Plane.as
 */

THREE.PlaneBufferGeometry = function ( width, height, widthSegments, heightSegments ) {

	THREE.BufferGeometry.call( this );

	this.parameters = {
		width: width,
		height: height,
		widthSegments: widthSegments,
		heightSegments: heightSegments
	};

	var width_half = width / 2;
	var height_half = height / 2;

	var gridX = widthSegments || 1;
	var gridY = heightSegments || 1;

	var gridX1 = gridX + 1;
	var gridY1 = gridY + 1;

	var segment_width = width / gridX;
	var segment_height = height / gridY;

	var vertices = new Float32Array( gridX1 * gridY1 * 3 );
	var normals = new Float32Array( gridX1 * gridY1 * 3 );
	var uvs = new Float32Array( gridX1 * gridY1 * 2 );

	var offset = 0;
	var offset2 = 0;

	for ( var iy = 0; iy < gridY1; iy ++ ) {

		var y = iy * segment_height - height_half;

		for ( var ix = 0; ix < gridX1; ix ++ ) {

			var x = ix * segment_width - width_half;

			vertices[ offset     ] = x;
			vertices[ offset + 1 ] = - y;

			normals[ offset + 2 ] = 1;

			uvs[ offset2     ] = ix / gridX;
			uvs[ offset2 + 1 ] = 1 - ( iy / gridY );

			offset += 3;
			offset2 += 2;

		}

	}

	offset = 0;

	var indices = new Uint16Array( gridX * gridY * 6 );

	for ( var iy = 0; iy < gridY; iy ++ ) {

		for ( var ix = 0; ix < gridX; ix ++ ) {

			var a = ix + gridX1 * iy;
			var b = ix + gridX1 * ( iy + 1 );
			var c = ( ix + 1 ) + gridX1 * ( iy + 1 );
			var d = ( ix + 1 ) + gridX1 * iy;

			indices[ offset     ] = a;
			indices[ offset + 1 ] = b;
			indices[ offset + 2 ] = d;

			indices[ offset + 3 ] = b;
			indices[ offset + 4 ] = c;
			indices[ offset + 5 ] = d;

			offset += 6;

		}

	}

	this.attributes[ 'index' ] = { array: indices, itemSize: 1 };
	this.attributes[ 'position' ] = { array: vertices, itemSize: 3 };
	this.attributes[ 'normal' ] = { array: normals, itemSize: 3 };
	this.attributes[ 'uv' ] = { array: uvs, itemSize: 2 };

};

THREE.PlaneBufferGeometry.prototype = Object.create( THREE.BufferGeometry.prototype );