updates [turf-ellipse] the distribution of points along the circumfer…

…ence is now optional. The default value for accuracy (0) leads to the same result as previously. Using custom values for accuracy will distribute points along the circumference (which is more precise for "thin" ellipses, but more expensive).
Turfjs · Nov 4, 2024 · f4ed1c5 · f4ed1c5
1 parent cad1832
commit f4ed1c5
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Showing 10 changed files with 1,145 additions and 1,130 deletions.
diff --git a/packages/turf-ellipse/index.ts b/packages/turf-ellipse/index.ts
@@ -56,7 +56,7 @@ function ellipse(
   const angle = options.angle || 0;
   const pivot = options.pivot || center;
   const properties = options.properties || {};
-  const accuracy = options.accuracy || 3;
+  const accuracy = options.accuracy === undefined ? 0 : options.accuracy;
   // validation
   if (!center) throw new Error("center is required");
   if (!xSemiAxis) throw new Error("xSemiAxis is required");
@@ -65,6 +65,10 @@ function ellipse(
   if (!isNumber(steps)) throw new Error("steps must be a number");
   if (!isNumber(angle)) throw new Error("angle must be a number");
   if (!isNumber(accuracy)) throw new Error("accuracy must be a number");
+  if (accuracy !== 0 && accuracy < 1)
+    throw new Error(
+      "accuracy must either be equal to -1 or greater or equal to 1"
+    );
 
   const internalSteps = Math.floor(Math.pow(accuracy, 2) * steps);
 
@@ -89,43 +93,47 @@ function ellipse(
   let previousCoords = currentCoords;
   const cumulatedArcLength = [0];
   const cumulatedAngle = [0];
-
-  for (let i = 1; i < internalSteps + 1; i += 1) {
-    previousCoords = currentCoords;
-    currentAngle = (360 * i) / internalSteps;
-    r = Math.sqrt(
-      (Math.pow(xSemiAxis, 2) * Math.pow(ySemiAxis, 2)) /
-        (Math.pow(
-          xSemiAxis * Math.cos(degreesToRadians(currentAngle - angle)),
-          2
-        ) +
-          Math.pow(
-            ySemiAxis * Math.sin(degreesToRadians(currentAngle - angle)),
+  let circumference = 0;
+  if (accuracy != 0) {
+    for (let i = 1; i < internalSteps + 1; i += 1) {
+      previousCoords = currentCoords;
+      currentAngle = (360 * i) / internalSteps;
+      r = Math.sqrt(
+        (Math.pow(xSemiAxis, 2) * Math.pow(ySemiAxis, 2)) /
+          (Math.pow(
+            xSemiAxis * Math.cos(degreesToRadians(currentAngle - angle)),
             2
-          ))
-    );
-    currentCoords = getCoord(
-      destination(centerCoords, r, currentAngle, { units: units })
-    );
-    currentArcLength += distance(previousCoords, currentCoords);
-    cumulatedAngle.push(currentAngle);
-    cumulatedArcLength.push(currentArcLength);
+          ) +
+            Math.pow(
+              ySemiAxis * Math.sin(degreesToRadians(currentAngle - angle)),
+              2
+            ))
+      );
+      currentCoords = getCoord(
+        destination(centerCoords, r, currentAngle, { units: units })
+      );
+      currentArcLength += distance(previousCoords, currentCoords);
+      cumulatedAngle.push(currentAngle);
+      cumulatedArcLength.push(currentArcLength);
+    }
+    circumference = cumulatedArcLength[cumulatedArcLength.length - 1];
   }
-  const circumference = cumulatedArcLength[cumulatedArcLength.length - 1];
 
   let j = 0;
   for (let i = 1; i < steps; i += 1) {
-    const targetArcLength = (i * circumference) / steps;
-    while (cumulatedArcLength[j] < targetArcLength) {
-      j += 1;
+    let angleNewPoint = (360 * i) / steps;
+    if (accuracy != 0) {
+      const targetArcLength = (i * circumference) / steps;
+      while (cumulatedArcLength[j] < targetArcLength) {
+        j += 1;
+      }
+      const ratio =
+        (targetArcLength - cumulatedArcLength[j - 1]) /
+        (cumulatedArcLength[j] - cumulatedArcLength[j - 1]);
+      angleNewPoint =
+        cumulatedAngle[j - 1] +
+        ratio * (cumulatedAngle[j] - cumulatedAngle[j - 1]);
     }
-    const ratio =
-      (targetArcLength - cumulatedArcLength[j - 1]) /
-      (cumulatedArcLength[j] - cumulatedArcLength[j - 1]);
-    const angleNewPoint =
-      cumulatedAngle[j - 1] +
-      ratio * (cumulatedAngle[j] - cumulatedAngle[j - 1]);
-
     r = Math.sqrt(
       (Math.pow(xSemiAxis, 2) * Math.pow(ySemiAxis, 2)) /
         (Math.pow(

diff --git a/packages/turf-ellipse/test.ts b/packages/turf-ellipse/test.ts
@@ -34,9 +34,15 @@ test("turf-ellipse", (t) => {
     const name = fixture.name;
     const geojson = fixture.geojson;
     const center = geojson.geometry.coordinates;
-    let { xSemiAxis, ySemiAxis, steps, angle, units } = geojson.properties;
+    let { xSemiAxis, ySemiAxis, steps, angle, units, accuracy } =
+      geojson.properties;
     angle = angle || 0;
-    const options = { steps, angle, units };
+    const options = {
+      steps: steps,
+      angle: angle,
+      units: units,
+      accuracy: accuracy,
+    };
     const maxAxis = Math.max(xSemiAxis, ySemiAxis);
 
     const results = featureCollection([
@@ -51,6 +57,7 @@ test("turf-ellipse", (t) => {
             steps,
             angle: angle + 90,
             units,
+            accuracy: accuracy,
           }),
           "#0F0"
         )

diff --git a/packages/turf-ellipse/test/out/anti-meridian-degrees.json b/packages/turf-ellipse/test/out/anti-meridian-degrees.json
@@ -107,69 +107,69 @@
         "coordinates": [
           [
             [-180, -7],
-            [-176.738849, -6.999277],
-            [-173.477813, -6.997315],
-            [-170.216821, -6.994743],
-            [-166.95618, -6.992655],
-            [-163.69532, -6.992682],
-            [-160.434971, -6.997114],
-            [-157.1736, -7.009093],
-            [-153.912019, -7.03292],
-            [-150.651306, -7.074538],
-            [-147.389796, -7.142453],
-            [-144.129317, -7.24924],
-            [-140.869431, -7.41491],
-            [-137.612939, -7.674292],
-            [-134.370698, -8.097871],
-            [-131.193938, -8.873656],
+            [-179.012909, -6.999932],
+            [-178.007657, -6.999726],
+            [-176.964769, -6.999372],
+            [-175.861944, -6.998853],
+            [-174.672095, -6.998147],
+            [-173.36058, -6.997228],
+            [-171.881019, -6.996076],
+            [-170.168666, -6.994705],
+            [-168.12949, -6.993261],
+            [-165.621642, -6.992297],
+            [-162.42371, -6.993735],
+            [-158.183237, -7.004346],
+            [-152.358412, -7.050082],
+            [-144.326578, -7.241357],
+            [-134.633424, -8.05423],
             [-128.744776, -10.832176],
-            [-130.085087, -13.650444],
-            [-132.686206, -15.685771],
-            [-135.569995, -17.374365],
-            [-138.601438, -18.853757],
-            [-141.736897, -20.175837],
-            [-144.956526, -21.3648],
-            [-148.250042, -22.433239],
-            [-151.607646, -23.386802],
-            [-155.024266, -24.22889],
-            [-158.492384, -24.960237],
-            [-162.004653, -25.580714],
-            [-165.555992, -26.090075],
-            [-169.138528, -26.487393],
-            [-172.745429, -26.771923],
-            [-176.368571, -26.94294],
+            [-132.913393, -15.833284],
+            [-141.929439, -20.251391],
+            [-150.000227, -22.946517],
+            [-156.092677, -24.46711],
+            [-160.62983, -25.351901],
+            [-164.098361, -25.895108],
+            [-166.841894, -26.24599],
+            [-169.085426, -26.482344],
+            [-170.976743, -26.646744],
+            [-172.615433, -26.763657],
+            [-174.070866, -26.847757],
+            [-175.393155, -26.908141],
+            [-176.619973, -26.950571],
+            [-177.78092, -26.9787],
+            [-178.900458, -26.994771],
             [-180, -27],
-            [-183.631429, -26.94294],
-            [-187.254571, -26.771923],
-            [-190.861472, -26.487393],
-            [-194.444008, -26.090075],
-            [-197.995347, -25.580714],
-            [-201.507616, -24.960237],
-            [-204.975734, -24.22889],
-            [-208.392354, -23.386802],
-            [-211.749958, -22.433239],
-            [-215.043474, -21.3648],
-            [-218.263103, -20.175837],
-            [-221.398562, -18.853757],
-            [-224.430005, -17.374365],
-            [-227.313794, -15.685771],
-            [-229.914913, -13.650444],
+            [-181.099542, -26.994771],
+            [-182.21908, -26.9787],
+            [-183.380027, -26.950571],
+            [-184.606845, -26.908141],
+            [-185.929134, -26.847757],
+            [-187.384567, -26.763657],
+            [-189.023257, -26.646744],
+            [-190.914574, -26.482344],
+            [-193.158106, -26.24599],
+            [-195.901639, -25.895108],
+            [-199.37017, -25.351901],
+            [-203.907323, -24.46711],
+            [-209.999773, -22.946517],
+            [-218.070561, -20.251391],
+            [-227.086607, -15.833284],
             [-231.255224, -10.832176],
-            [-228.806062, -8.873656],
-            [-225.629302, -8.097871],
-            [-222.387061, -7.674292],
-            [-219.130569, -7.41491],
-            [-215.870683, -7.24924],
-            [-212.610204, -7.142453],
-            [-209.348694, -7.074538],
-            [-206.087981, -7.03292],
-            [-202.8264, -7.009093],
-            [-199.565029, -6.997114],
-            [-196.30468, -6.992682],
-            [-193.04382, -6.992655],
-            [-189.783179, -6.994743],
-            [-186.522187, -6.997315],
-            [-183.261151, -6.999277],
+            [-225.366576, -8.05423],
+            [-215.673422, -7.241357],
+            [-207.641588, -7.050082],
+            [-201.816763, -7.004346],
+            [-197.57629, -6.993735],
+            [-194.378358, -6.992297],
+            [-191.87051, -6.993261],
+            [-189.831334, -6.994705],
+            [-188.118981, -6.996076],
+            [-186.63942, -6.997228],
+            [-185.327905, -6.998147],
+            [-184.138056, -6.998853],
+            [-183.035231, -6.999372],
+            [-181.992343, -6.999726],
+            [-180.987091, -6.999932],
             [-180, -7]
           ]
         ]
@@ -188,69 +188,69 @@
         "coordinates": [
           [
             [-180, 33],
-            [-177.140393, 31.055266],
-            [-175.597566, 28.11005],
-            [-174.534874, 25.013207],
-            [-173.72227, 21.861462],
-            [-173.066567, 18.682944],
-            [-172.519156, 15.488953],
-            [-172.050878, 12.283875],
-            [-171.64316, 9.072469],
-            [-171.282867, 5.855031],
-            [-170.960895, 2.633936],
-            [-170.670524, -0.589097],
-            [-170.406554, -3.814932],
-            [-170.165253, -7.042382],
-            [-169.943765, -10.271676],
-            [-169.740098, -13.502271],
+            [-175.497882, 27.861418],
+            [-173.030729, 18.490068],
+            [-171.830809, 10.60333],
+            [-171.179456, 4.858227],
+            [-170.780383, 0.668263],
+            [-170.511657, -2.494484],
+            [-170.317281, -4.976107],
+            [-170.168666, -6.994705],
+            [-170.049885, -8.690233],
+            [-169.951409, -10.15556],
+            [-169.867192, -11.454674],
+            [-169.7932, -12.633439],
+            [-169.726611, -13.726124],
+            [-169.665366, -14.759536],
+            [-169.607893, -15.755753],
             [-169.55293, -16.734064],
-            [-169.381609, -19.966817],
-            [-169.226157, -23.200324],
-            [-169.087344, -26.434579],
-            [-168.966868, -29.669207],
-            [-168.867575, -32.904694],
-            [-168.79396, -36.140205],
-            [-168.752764, -39.377096],
-            [-168.754199, -42.614301],
-            [-168.813714, -45.850315],
-            [-168.955371, -49.086046],
-            [-169.217769, -52.318336],
-            [-169.666488, -55.545023],
-            [-170.421106, -58.757802],
-            [-171.726422, -61.932319],
-            [-174.201492, -64.97435],
+            [-169.499415, -17.712463],
+            [-169.446396, -18.70895],
+            [-169.39297, -19.742835],
+            [-169.338231, -20.836238],
+            [-169.281216, -22.016028],
+            [-169.220871, -23.316582],
+            [-169.156026, -24.783931],
+            [-169.085426, -26.482344],
+            [-169.007959, -28.505179],
+            [-168.923458, -30.993289],
+            [-168.835498, -34.16656],
+            [-168.761519, -38.375012],
+            [-168.77409, -44.156217],
+            [-169.197442, -52.122889],
+            [-171.589247, -61.67665],
             [-180, -67],
-            [-185.798508, -64.97435],
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+            [-189.831334, -6.994705],
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+            [-189.488343, -2.494484],
+            [-189.219617, 0.668263],
+            [-188.820544, 4.858227],
+            [-188.169191, 10.60333],
+            [-186.969271, 18.490068],
+            [-184.502118, 27.861418],
             [-180, 33]
           ]
         ]