fix fill extrusion querying for colinear points (#9454)

When checking for intersections with a fill-extrusion it has to calculate the distance to the plane the polygon exist on. If the first points of the geometry were colinear this calculation would fail. It now: - finds two distinct starting points a, b - loops over all the remaining vertices looking for a value that is not colinear with a, b Usually this will be the first vertex it encounters.
mapbox · Mar 24, 2020 · 0e04a3a · 0e04a3a
1 parent eeab959
commit 0e04a3a
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Showing 3 changed files with 133 additions and 20 deletions.
diff --git a/src/style/style_layer/fill_extrusion_style_layer.js b/src/style/style_layer/fill_extrusion_style_layer.js
@@ -81,34 +81,40 @@ export function getIntersectionDistance(projectedQueryGeometry: Array<Point>, pr
         // Check whether points are coincident and use other points if they are.
         let i = 0;
         const a = projectedFace[i++];
-        let b, c;
+        let b;
         while (!b || a.equals(b)) {
             b = projectedFace[i++];
             if (!b) return Infinity;
         }
-        while (!c || a.equals(c) || b.equals(c)) {
-            c = projectedFace[i++];
-            if (!c) return Infinity;
-        }
 
-        const p = projectedQueryGeometry[0];
+        // Loop until point `c` is not colinear with points `a` and `b`.
+        for (; i < projectedFace.length; i++) {
+            const c = projectedFace[i];
+
+            const p = projectedQueryGeometry[0];
+
+            const ab = b.sub(a);
+            const ac = c.sub(a);
+            const ap = p.sub(a);
 
-        const ab = b.sub(a);
-        const ac = c.sub(a);
-        const ap = p.sub(a);
+            const dotABAB = dot(ab, ab);
+            const dotABAC = dot(ab, ac);
+            const dotACAC = dot(ac, ac);
+            const dotAPAB = dot(ap, ab);
+            const dotAPAC = dot(ap, ac);
+            const denom = dotABAB * dotACAC - dotABAC * dotABAC;
 
-        const dotABAB = dot(ab, ab);
-        const dotABAC = dot(ab, ac);
-        const dotACAC = dot(ac, ac);
-        const dotAPAB = dot(ap, ab);
-        const dotAPAC = dot(ap, ac);
-        const denom = dotABAB * dotACAC - dotABAC * dotABAC;
-        const v = (dotACAC * dotAPAB - dotABAC * dotAPAC) / denom;
-        const w = (dotABAB * dotAPAC - dotABAC * dotAPAB) / denom;
-        const u = 1 - v - w;
+            const v = (dotACAC * dotAPAB - dotABAC * dotAPAC) / denom;
+            const w = (dotABAB * dotAPAC - dotABAC * dotAPAB) / denom;
+            const u = 1 - v - w;
+
+            // Use the barycentric weighting along with the original triangle z coordinates to get the point of intersection.
+            const distance = a.z * u + b.z * v + c.z * w;
+
+            if (isFinite(distance)) return distance;
+        }
 
-        // Use the barycentric weighting along with the original triangle z coordinates to get the point of intersection.
-        return a.z * u + b.z * v + c.z * w;
+        return Infinity;
 
     } else {
         // The counts as closest is less clear when the query is a box. This

diff --git a/test/integration/query-tests/regressions/mapbox-gl-js#8999-2/expected.json b/test/integration/query-tests/regressions/mapbox-gl-js#8999-2/expected.json
@@ -0,0 +1,37 @@
+[
+  {
+    "geometry": {
+      "type": "Polygon",
+      "coordinates": [
+        [
+          [
+            -19.9951171875,
+            -40.01078714046552
+          ],
+          [
+            -19.9951171875,
+            40.01078714046551
+          ],
+          [
+            -19.9951171875,
+            59.99898612060443
+          ],
+          [
+            19.9951171875,
+            20.014645445341372
+          ],
+          [
+            -19.9951171875,
+            -40.01078714046552
+          ]
+        ]
+      ]
+    },
+    "type": "Feature",
+    "properties": {
+      "layer": "extrusion_colinear_points"
+    },
+    "source": "extrusion_colinear_points",
+    "state": {}
+  }
+]
diff --git a/test/integration/query-tests/regressions/mapbox-gl-js#8999-2/style.json b/test/integration/query-tests/regressions/mapbox-gl-js#8999-2/style.json
@@ -0,0 +1,70 @@
+{
+  "version": 8,
+  "metadata": {
+    "test": {
+      "debug": true,
+      "width": 200,
+      "height": 200,
+      "queryGeometry": [
+          100,
+          40
+      ]
+    }
+  },
+  "pitch": 0,
+  "center": [
+      0,
+      0
+  ],
+  "zoom": 0,
+  "sources": {
+    "extrusion_colinear_points": {
+      "type": "geojson",
+        "tolerance": 0,
+        "data": {
+            "type": "Feature",
+            "properties": {
+                "layer": "extrusion_colinear_points"
+            },
+            "geometry": {
+                "type": "Polygon",
+                "coordinates": [
+                    [
+                        [
+                            -20,
+                            -40
+                        ],
+                        [
+                            -20,
+                            40
+                        ],
+                        [
+                            -20,
+                            60
+                        ],
+                        [
+                            20,
+                            20
+                        ],
+                        [
+                            -20,
+                            -40
+                        ]
+                    ]
+                ]
+            }
+        }
+	}
+  },
+  "layers": [
+    {
+      "id": "extrusion_colinear_points",
+      "type": "fill-extrusion",
+      "source": "extrusion_colinear_points",
+      "paint": {
+        "fill-extrusion-color": "#ecc",
+        "fill-extrusion-height": 0
+      }
+    }
+  ]
+}