const flatten = require('../utils/flatten')
const geom2 = require('../geometries/geom2')
const geom3 = require('../geometries/geom3')
const path2 = require('../geometries/path2')
const poly3 = require('../geometries/poly3')
const cache = new WeakMap()
/*
* Measure the area of the given geometry.
* NOTE: paths are infinitely narrow and do not have an area
*
* @param {path2} geometry - geometry to measure
* @returns {Number} area of the geometry
*/
const measureAreaOfPath2 = () => 0
/*
* Measure the area of the given geometry.
* For a counter clockwise rotating geometry (about Z) the area is positive, otherwise negative.
*
* @see http://paulbourke.net/geometry/polygonmesh/
* @param {geom2} geometry - 2D geometry to measure
* @returns {Number} area of the geometry
*/
const measureAreaOfGeom2 = (geometry) => {
let area = cache.get(geometry)
if (area) return area
const sides = geom2.toSides(geometry)
area = sides.reduce((area, side) => area + (side[0][0] * side[1][1] - side[0][1] * side[1][0]), 0)
area *= 0.5
cache.set(geometry, area)
return area
}
/*
* Measure the area of the given geometry.
*
* @param {geom3} geometry - 3D geometry to measure
* @returns {Number} area of the geometry
*/
const measureAreaOfGeom3 = (geometry) => {
let area = cache.get(geometry)
if (area) return area
const polygons = geom3.toPolygons(geometry)
area = polygons.reduce((area, polygon) => area + poly3.measureArea(polygon), 0)
cache.set(geometry, area)
return area
}
/**
* Measure the area of the given geometries.
* @param {...Objects} geometries - the geometries to measure
* @return {Number|Array} the area, or a list of areas for each geometry
* @alias module:modeling/measurements.measureArea
*
* @example
* let area = measureArea(sphere())
*/
const measureArea = (...geometries) => {
geometries = flatten(geometries)
if (geometries.length === 0) throw new Error('wrong number of arguments')
const results = geometries.map((geometry) => {
if (path2.isA(geometry)) return measureAreaOfPath2(geometry)
if (geom2.isA(geometry)) return measureAreaOfGeom2(geometry)
if (geom3.isA(geometry)) return measureAreaOfGeom3(geometry)
return 0
})
return results.length === 1 ? results[0] : results
}
module.exports = measureArea