Cylinder.js

var MeshData = require('../renderer/MeshData');
var Vector3 = require('../math/Vector3');
var ObjectUtils = require('../util/ObjectUtils');

/**
 * A 3D object representing a cylinder.
 * @extends MeshData
 * @param {number} [radialSamples=8] Number of slices
 * @param {number} [radiusTop=0.5] Radius of the cylinder at the top.
 * @param {number} [radiusBottom=radiusTop] Radius of the cylinder at the bottom. Defaults to radiusTop.
 * @param {number} [height=1] Height
 */
function Cylinder(radialSamples, radiusTop, radiusBottom, height) {
	if (arguments.length === 1 && arguments[0] instanceof Object) {
		var props = arguments[0];
		radialSamples = props.radialSamples;
		radiusTop = props.radiusTop;
		radiusBottom = props.radiusBottom;
		height = props.height;
	}
	this.radialSamples = radialSamples || 8;
	this.radiusTop = typeof radiusTop === 'undefined' ? 0.5 : radiusTop;
	this.radiusBottom = typeof radiusBottom === 'undefined' ? this.radiusTop : radiusBottom;
	this.height = typeof height === 'undefined' ? 1 : height;

	var attributeMap = MeshData.defaultMap([MeshData.POSITION, MeshData.NORMAL, MeshData.TEXCOORD0]);
	MeshData.call(this, attributeMap, this.radialSamples * 4 + 2 + 2, (this.radialSamples * 3) * 4);

	// could be done better with 2 triangle fans and a triangle strip
	this.indexModes = ['Triangles'];

	this.rebuild();
}

Cylinder.prototype = Object.create(MeshData.prototype);
Cylinder.prototype.constructor = Cylinder;

/**
 * Builds or rebuilds the mesh data.
 * @returns {Cylinder} Self for chaining.
 */
Cylinder.prototype.rebuild = function () {
	var verts = [];
	var norms = [];
	var tex = [];
	var indices = [];
	var height = this.height;
	var halfHeight = height / 2;
	var radiusTop = this.radiusTop;
	var radiusBottom = this.radiusBottom;
	var radialSamples = this.radialSamples;

	var ak = Math.PI * 2 / radialSamples;
	var at = 1 / radialSamples;

	var lastIndex = radialSamples * 4 + 2 + 2 - 1;
	var normal = new Vector3();

	var tan = 0;
	if (height) {
		tan = Math.tan((radiusBottom - radiusTop) / height);
	}

	for (var i = 0, k = 0, t = 0; i < radialSamples; i++, k += ak, t += at) {
		var cos = Math.cos(k);
		var sin = Math.sin(k);
		var xTop = cos * radiusTop;
		var yTop = sin * radiusTop;
		var xBottom = cos * radiusBottom;
		var yBottom = sin * radiusBottom;

		verts.push(
			xTop, yTop, halfHeight, // disk top
			xBottom, yBottom, -halfHeight, // disk bottom
			xTop, yTop, halfHeight,  // side top
			xBottom, yBottom, -halfHeight  // side bottom
		);

		normal.setDirect(cos, sin, tan);
		normal.normalize();

		norms.push(
			0, 0, 1,
			0, 0, -1,
			normal.x, normal.y, normal.z,
			normal.x, normal.y, normal.z
			//cos, sin, 0,
			//cos, sin, 0
		);

		tex.push(
			cos / 4 + 0.25, sin / 4 + 0.75,
			cos / 4 + 0.25, sin / 4 + 0.25,
			0.5, t,
			1.0, t
		);
	}

	verts.push(
		radiusTop, 0.0, halfHeight,
		radiusBottom, 0.0, -halfHeight
	);

	norms.push(
		1.0, 0.0, 0.0,
		1.0, 0.0, 0.0
	);

	tex.push(
		0.5, 1.0,
		1.0, 1.0
	);

	for (var i = 0; i < radialSamples - 1; i++) {
		indices.push(
			lastIndex, i * 4 + 0, i * 4 + 4,
			i * 4 + 1, lastIndex - 1, i * 4 + 5,
			i * 4 + 4 + 2, i * 4 + 2, i * 4 + 4 + 3,
			i * 4 + 2, i * 4 + 3, i * 4 + 4 + 3
		);
	}

	indices.push(
		lastIndex, i * 4 + 0, 0,
		i * 4 + 1, lastIndex - 1, 0 + 1,
		i * 4 + 4, i * 4 + 2, i * 4 + 5,
		i * 4 + 2, i * 4 + 3, i * 4 + 5
	);

	verts.push(
		0, 0, -halfHeight,
		0, 0, halfHeight
	);

	norms.push(
		0, 0, -0.5,
		0, 0, 0.5
	);

	tex.push(
		0.25, 0.25,
		0.25, 0.75
	);

	this.getAttributeBuffer(MeshData.POSITION).set(verts);
	this.getAttributeBuffer(MeshData.NORMAL).set(norms);
	this.getAttributeBuffer(MeshData.TEXCOORD0).set(tex);
	this.getIndexBuffer().set(indices);

	return this;
};

/**
 * Returns a clone of this cylinder
 * @returns {Cylinder}
 */
Cylinder.prototype.clone = function () {
	var options = ObjectUtils.shallowSelectiveClone(this, ['radialSamples', 'radiusTop', 'radiusBottom', 'height']);

	return new Cylinder(options);
};

module.exports = Cylinder;