289 lines
7.4 KiB
JavaScript
289 lines
7.4 KiB
JavaScript
import bSpline from './util/bSpline'
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import logger from './util/logger'
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import createArcForLWPolyine from './util/createArcForLWPolyline'
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/**
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* Rotate a set of points.
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*
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* @param points the points
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* @param angle the rotation angle
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*/
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const rotate = (points, angle) => {
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return points.map(function (p) {
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return [
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p[0] * Math.cos(angle) - p[1] * Math.sin(angle),
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p[1] * Math.cos(angle) + p[0] * Math.sin(angle),
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]
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})
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}
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/**
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* Interpolate an ellipse
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* @param cx center X
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* @param cy center Y
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* @param rx radius X
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* @param ry radius Y
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* @param start start angle in radians
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* @param start end angle in radians
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*/
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const interpolateEllipse = (cx, cy, rx, ry, start, end, rotationAngle) => {
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if (end < start) {
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end += Math.PI * 2
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}
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// ----- Relative points -----
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// Start point
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let points = []
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const dTheta = (Math.PI * 2) / 72
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const EPS = 1e-6
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for (let theta = start; theta < end - EPS; theta += dTheta) {
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points.push([Math.cos(theta) * rx, Math.sin(theta) * ry])
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}
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points.push([Math.cos(end) * rx, Math.sin(end) * ry])
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// ----- Rotate -----
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if (rotationAngle) {
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points = rotate(points, rotationAngle)
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}
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// ----- Offset center -----
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points = points.map(function (p) {
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return [cx + p[0], cy + p[1]]
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})
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return points
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}
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/**
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* Interpolate a b-spline. The algorithm examins the knot vector
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* to create segments for interpolation. The parameterisation value
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* is re-normalised back to [0,1] as that is what the lib expects (
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* and t i de-normalised in the b-spline library)
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*
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* @param controlPoints the control points
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* @param degree the b-spline degree
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* @param knots the knot vector
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* @returns the polyline
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*/
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export const interpolateBSpline = (
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controlPoints,
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degree,
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knots,
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interpolationsPerSplineSegment,
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weights,
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) => {
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const polyline = []
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const controlPointsForLib = controlPoints.map(function (p) {
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return [p.x, p.y]
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})
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const segmentTs = [knots[degree]]
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const domain = [knots[degree], knots[knots.length - 1 - degree]]
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for (let k = degree + 1; k < knots.length - degree; ++k) {
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if (segmentTs[segmentTs.length - 1] !== knots[k]) {
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segmentTs.push(knots[k])
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}
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}
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interpolationsPerSplineSegment = interpolationsPerSplineSegment || 25
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for (let i = 1; i < segmentTs.length; ++i) {
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const uMin = segmentTs[i - 1]
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const uMax = segmentTs[i]
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for (let k = 0; k <= interpolationsPerSplineSegment; ++k) {
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const u = (k / interpolationsPerSplineSegment) * (uMax - uMin) + uMin
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// Clamp t to 0, 1 to handle numerical precision issues
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let t = (u - domain[0]) / (domain[1] - domain[0])
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t = Math.max(t, 0)
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t = Math.min(t, 1)
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const p = bSpline(t, degree, controlPointsForLib, knots, weights)
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polyline.push(p)
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}
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}
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return polyline
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}
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export const polyfaceOutline = (entity) => {
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const vertices = []
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const faces = []
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for (const v of entity.vertices) {
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if (v.faces) {
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const face = { indices: [], hiddens: [] }
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for (const i of v.faces) {
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if (i === 0) {
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break
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}
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// Negative indices signify hidden edges
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face.indices.push(i < 0 ? -i - 1 : i - 1)
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face.hiddens.push(i < 0)
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}
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if ([3, 4].includes(face.indices.length)) faces.push(face)
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} else {
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vertices.push({ x: v.x, y: v.y })
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}
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}
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// If a segment starts at the end of a previous line, continue it
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const polylines = []
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const segment = (a, b) => {
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for (const prev of polylines) {
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if (prev.slice(-1)[0] === a) {
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return prev.push(b)
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}
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}
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polylines.push([a, b])
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}
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for (const face of faces) {
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for (let beg = 0; beg < face.indices.length; beg++) {
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if (face.hiddens[beg]) {
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continue
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}
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const end = (beg + 1) % face.indices.length
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segment(face.indices[beg], face.indices[end])
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}
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}
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// Sometimes segments are not sequential, in that case
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// we need to find if they can mend gaps between others
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for (const a of polylines) {
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for (const b of polylines) {
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if (a !== b && a[0] === b.slice(-1)[0]) {
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b.push(...a.slice(1))
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a.splice(0, a.length)
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break
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}
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}
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}
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return polylines
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.filter((l) => l.length)
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.map((l) => l.map((i) => vertices[i]).map((v) => [v.x, v.y]))
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}
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/**
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* Convert a parsed DXF entity to a polyline. These can be used to render the
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* the DXF in SVG, Canvas, WebGL etc., without depending on native support
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* of primitive objects (ellispe, spline etc.)
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*/
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export default (entity, options) => {
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options = options || {}
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let polyline
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if (entity.type === 'LINE') {
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polyline = [
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[entity.start.x, entity.start.y],
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[entity.end.x, entity.end.y],
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]
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}
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if (entity.type === 'LWPOLYLINE' || entity.type === 'POLYLINE') {
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polyline = []
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if (entity.polyfaceMesh) {
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// Only return the first polyline because we can't return many
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polyline.push(...polyfaceOutline(entity)[0])
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} else if (entity.polygonMesh) {
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// Do not attempt to render polygon meshes
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} else if (entity.vertices.length) {
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if (entity.closed) {
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entity.vertices = entity.vertices.concat(entity.vertices[0])
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}
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for (let i = 0, il = entity.vertices.length; i < il - 1; ++i) {
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const from = [entity.vertices[i].x, entity.vertices[i].y]
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const to = [entity.vertices[i + 1].x, entity.vertices[i + 1].y]
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polyline.push(from)
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if (entity.vertices[i].bulge) {
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polyline = polyline.concat(
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createArcForLWPolyine(from, to, entity.vertices[i].bulge),
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)
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}
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// The last iteration of the for loop
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if (i === il - 2) {
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polyline.push(to)
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}
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}
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} else {
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logger.warn('Polyline entity with no vertices')
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}
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}
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if (entity.type === 'CIRCLE') {
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polyline = interpolateEllipse(
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entity.x,
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entity.y,
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entity.r,
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entity.r,
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0,
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Math.PI * 2,
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)
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if (entity.extrusionZ === -1) {
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polyline = polyline.map(function (p) {
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return [-p[0], p[1]]
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})
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}
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}
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if (entity.type === 'ELLIPSE') {
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const rx = Math.sqrt(
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entity.majorX * entity.majorX + entity.majorY * entity.majorY,
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)
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const ry = entity.axisRatio * rx
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const majorAxisRotation = -Math.atan2(-entity.majorY, entity.majorX)
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polyline = interpolateEllipse(
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entity.x,
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entity.y,
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rx,
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ry,
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entity.startAngle,
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entity.endAngle,
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majorAxisRotation,
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)
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if (entity.extrusionZ === -1) {
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polyline = polyline.map(function (p) {
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return [-p[0], p[1]]
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})
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}
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}
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if (entity.type === 'ARC') {
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// Why on earth DXF has degree start & end angles for arc,
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// and radian start & end angles for ellipses is a mystery
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polyline = interpolateEllipse(
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entity.x,
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entity.y,
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entity.r,
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entity.r,
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entity.startAngle,
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entity.endAngle,
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undefined,
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false,
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)
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// I kid you not, ARCs and ELLIPSEs handle this differently,
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// as evidenced by how AutoCAD actually renders these entities
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if (entity.extrusionZ === -1) {
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polyline = polyline.map(function (p) {
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return [-p[0], p[1]]
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})
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}
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}
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if (entity.type === 'SPLINE') {
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polyline = interpolateBSpline(
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entity.controlPoints,
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entity.degree,
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entity.knots,
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options.interpolationsPerSplineSegment,
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entity.weights,
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)
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}
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if (!polyline) {
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logger.warn('unsupported entity for converting to polyline:', entity.type)
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return []
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}
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return polyline
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}
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