first steps at ensuring coincident-point? works for edge intersections

dgtized · May 29, 2024 · b38254b · b38254b
1 parent 7f45ca1
commit b38254b
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Showing 2 changed files with 17 additions and 8 deletions.
diff --git a/src/shimmers/math/geometry/collisions.cljc b/src/shimmers/math/geometry/collisions.cljc
@@ -344,13 +344,17 @@
 ;; FIXME shoudl this be iff, ie only the case if coincident-point is unique?
 (defmulti coincident-point?
   "Test if shapes `a` and `b` share a single point in common, either at a vertice or along
-  an intersecting edge."
+  an intersecting edge. Returns contact point if touching"
   (fn [a b] [(type a) (type b)]))
 
+;; FIXME: This includes cases where polygons just intersect eachother
 (defmethod coincident-point?
   [Polygon2 Polygon2] [a b]
-  (some (fn [[ap bp]] (tm/delta= ap bp))
-        (mc/cartesian-product (g/vertices a) (g/vertices b))))
+  (or (some (fn [[ap bp]] (when (tm/delta= ap bp) ap))
+            (mc/cartesian-product (g/vertices a) (g/vertices b)))
+      (some (fn [[a-edge b-edge]]
+              (intersect/segment-intersect a-edge b-edge))
+            (mc/cartesian-product (g/edges a) (g/edges b)))))
 
 (defmulti adjacent?
   "Test if shapes `a` and `b` share a vertice or an edge, but do not intersect inside."

diff --git a/test/shimmers/math/geometry/collisions_test.cljc b/test/shimmers/math/geometry/collisions_test.cljc
@@ -8,7 +8,8 @@
    [thi.ng.geom.line :as gl]
    [thi.ng.geom.polygon :as gp]
    [thi.ng.geom.rect :as rect]
-   [thi.ng.geom.vector :as gv]))
+   [thi.ng.geom.vector :as gv]
+   [thi.ng.math.core :as tm]))
 
 (deftest overlap?
   (t/testing "Rect2 Rect2"
@@ -50,7 +51,11 @@
 
 (deftest coincident-point?
   (t/testing "Polygon2 Polygon2"
-    (is (not (sut/coincident-point? (gp/polygon2 [0.1 0] [5 0.2] [2.5 3])
-                                    (gp/polygon2 [0.0 0] [5 0.3] [2.5 -3]))))
-    (is (sut/coincident-point? (gp/polygon2 [0.1 0] [5 0.2] [2.5 3])
-                               (gp/polygon2 [0.0 0] [5 0.2] [2.5 -3])))))
+    (is (nil? (sut/coincident-point? (gp/polygon2 [0.0 1] [5 2] [2.5 3])
+                                     (gp/polygon2 [0.0 0] [5 0] [2.5 -3]))))
+    (is (tm/delta= (sut/coincident-point? (gp/polygon2 [0.1 0] [5 0.2] [2.5 3])
+                                          (gp/polygon2 [0.0 0] [5 0.2] [2.5 -3]))
+                   [5 0.2]))
+    (is (tm/delta= (sut/coincident-point? (gp/polygon2 [0 0] [10 0] [5 -5])
+                                          (gp/polygon2 [5 0] [10 5] [0 5]))
+                   [5 0]))))