three/src/extras/geometries/LatheBufferGeometry.js

JavaScript 3D library

/**
 * @author Mugen87 / https://github.com/Mugen87
 */

 // points - to create a closed torus, one must use a set of points
 //    like so: [ a, b, c, d, a ], see first is the same as last.
 // segments - the number of circumference segments to create
 // phiStart - the starting radian
 // phiLength - the radian (0 to 2PI) range of the lathed section
 //    2PI is a closed lathe, less than 2PI is a portion.

THREE.LatheBufferGeometry = function ( points, segments, phiStart, phiLength ) {

	THREE.BufferGeometry.call( this );

	this.type = 'LatheBufferGeometry';

	this.parameters = {
		points: points,
		segments: segments,
		phiStart: phiStart,
		phiLength: phiLength
	};

	segments = Math.floor( segments ) || 12;
	phiStart = phiStart || 0;
	phiLength = phiLength || Math.PI * 2;

	// clamp phiLength so it's in range of [ 0, 2PI ]
	phiLength = THREE.Math.clamp( phiLength, 0, Math.PI * 2 );

	// these are used to calculate buffer length
	var vertexCount = ( segments + 1 ) * points.length;
	var indexCount = segments * points.length * 2 * 3;

	// buffers
	var indices = new THREE.BufferAttribute( new ( indexCount > 65535 ? Uint32Array : Uint16Array )( indexCount ) , 1 );
	var vertices = new THREE.BufferAttribute( new Float32Array( vertexCount * 3 ), 3 );
	var uvs = new THREE.BufferAttribute( new Float32Array( vertexCount * 2 ), 2 );

	// helper variables
	var index = 0, indexOffset = 0, base;
	var inversePointLength = 1.0 / ( points.length - 1 );
	var inverseSegments = 1.0 / segments;
	var vertex = new THREE.Vector3();
	var uv = new THREE.Vector2();
	var i, j;

	// generate vertices and uvs

	for ( i = 0; i <= segments; i ++ ) {

		var phi = phiStart + i * inverseSegments * phiLength;

		var sin = Math.sin( phi );
		var cos = Math.cos( phi );

		for ( j = 0; j <= ( points.length - 1 ); j ++ ) {

			// vertex
			vertex.x = points[ j ].x * sin;
			vertex.y = points[ j ].y;
			vertex.z = points[ j ].x * cos;
			vertices.setXYZ( index, vertex.x, vertex.y, vertex.z );

			// uv
			uv.x = i / segments;
			uv.y = j / ( points.length - 1 );
			uvs.setXY( index, uv.x, uv.y );

			// increase index
			index ++;

		}

	}

	// generate indices

	for ( i = 0; i < segments; i ++ ) {

		for ( j = 0; j < ( points.length - 1 ); j ++ ) {

			base = j + i * points.length;

			// indices
			var a = base;
			var b = base + points.length;
			var c = base + points.length + 1;
			var d = base + 1;

			// face one
			indices.setX( indexOffset, a ); indexOffset++;
			indices.setX( indexOffset, b ); indexOffset++;
			indices.setX( indexOffset, d ); indexOffset++;

			// face two
			indices.setX( indexOffset, b ); indexOffset++;
			indices.setX( indexOffset, c ); indexOffset++;
			indices.setX( indexOffset, d ); indexOffset++;

		}

	}

	// build geometry

	this.setIndex( indices );
	this.addAttribute( 'position', vertices );
	this.addAttribute( 'uv', uvs );

	// generate normals

	this.computeVertexNormals();

	// if the geometry is closed, we need to average the normals along the seam.
	// because the corresponding vertices are identical (but still have different UVs).

	if( phiLength === Math.PI * 2 ) {

		var normals = this.attributes.normal.array;
		var n1 = new THREE.Vector3();
		var n2 = new THREE.Vector3();
		var n = new THREE.Vector3();

		// this is the buffer offset for the last line of vertices
		base = segments * points.length * 3;

		for( i = 0, j = 0; i < points.length; i ++, j += 3 ) {

			// select the normal of the vertex in the first line
			n1.x = normals[ j + 0 ];
			n1.y = normals[ j + 1 ];
			n1.z = normals[ j + 2 ];

			// select the normal of the vertex in the last line
			n2.x = normals[ base + j + 0 ];
			n2.y = normals[ base + j + 1 ];
			n2.z = normals[ base + j + 2 ];

			// average normals
			n.addVectors( n1, n2 ).normalize();

			// assign the new values to both normals
			normals[ j + 0 ] = normals[ base + j + 0 ] = n.x;
			normals[ j + 1 ] = normals[ base + j + 1 ] = n.y;
			normals[ j + 2 ] = normals[ base + j + 2 ] = n.z;

		} // next row

	}

};

THREE.LatheBufferGeometry.prototype = Object.create( THREE.BufferGeometry.prototype );
THREE.LatheBufferGeometry.prototype.constructor = THREE.LatheBufferGeometry;