Geom.Intersects.GetLineToPolygon is a new function that checks for the closest point of intersection between a line segment and an array of polygons.

Author: photonstorm

src/geom/intersects/GetLineToPolygon.js

@@ -0,0 +1,87 @@
+/**
+ * @author       Richard Davey
+ * @copyright    2020 Photon Storm Ltd.
+ * @license      {@link https://opensource.org/licenses/MIT|MIT License}
+ */
+
+var Vector3 = require('../../math/Vector3');
+var Vector4 = require('../../math/Vector4');
+var GetLineToLine = require('./GetLineToLine');
+var Line = require('../line/Line');
+
+//  Temp calculation segment
+var segment = new Line();
+
+//  Temp vec3
+var tempIntersect = new Vector3();
+
+/**
+ * Checks for the closest point of intersection between a line segment and an array of polygons.
+ *
+ * If no intersection is found, this function returns `null`.
+ *
+ * If intersection was found, a Vector4 is returned with the following properties:
+ *
+ * The `x` and `y` components contain the point of the intersection.
+ * The `z` component contains the closest distance.
+ * The `w` component contains the index of the polygon, in the given array, that triggered the intersection.
+ *
+ * @function Phaser.Geom.Intersects.GetLineToPolygon
+ * @since 3.25.0
+ *
+ * @param {Phaser.Geom.Line} line - The line segment to check.
+ * @param {Phaser.Geom.Polygon | Phaser.Geom.Polygon[]} polygons - A single polygon, or array of polygons, to check.
+ * @param {Phaser.Math.Vector4} [out] - A Vector4 to store the intersection results in.
+ *
+ * @return {Phaser.Math.Vector4} A Vector4 containing the intersection results, or `null`.
+ */
+var GetLineToPolygon = function (line, polygons, out)
+{
+    if (out === undefined)
+    {
+        out = new Vector4();
+    }
+
+    if (!Array.isArray(polygons))
+    {
+        polygons = [ polygons ];
+    }
+
+    var closestIntersect = false;
+
+    //  Reset our temporary vec4
+    tempIntersect.set();
+
+    for (var p = 0; p < polygons.length; p++)
+    {
+        var points = polygons[p].points;
+
+        var prev = points[0];
+
+        for (var i = 1; i < points.length; i++)
+        {
+            var current = points[i];
+
+            segment.setTo(prev.x, prev.y, current.x, current.y);
+
+            prev = current;
+
+            if (!GetLineToLine(line, segment, tempIntersect))
+            {
+                //  No intersection? Carry on ...
+                continue;
+            }
+
+            if (!closestIntersect || tempIntersect.z < out.z)
+            {
+                out.set(tempIntersect.x, tempIntersect.y, tempIntersect.z, p);
+
+                closestIntersect = true;
+            }
+        }
+    }
+
+    return (closestIntersect) ? out : null;
+};
+
+module.exports = GetLineToPolygon;

src/geom/intersects/index.js

@@ -16,6 +16,7 @@ module.exports = {
     GetCircleToRectangle: require('./GetCircleToRectangle'),
     GetLineToCircle: require('./GetLineToCircle'),
     GetLineToLine: require('./GetLineToLine'),
+    GetLineToPolygon: require('./GetLineToPolygon'),
     GetLineToRectangle: require('./GetLineToRectangle'),
     GetRectangleIntersection: require('./GetRectangleIntersection'),
     GetRectangleToRectangle: require('./GetRectangleToRectangle'),