Data commit

Task/Determine-if-two-triangles-overlap/F-Sharp/determine-if-two-triangles-overlap.fs

@@ -0,0 +1,99 @@
+open System
+
+type Point = double * double
+type Triangle = Point * Point * Point
+
+let Det2D (t:Triangle) =
+    let (p1, p2, p3) = t
+    let (p1x, p1y) = p1
+    let (p2x, p2y) = p2
+    let (p3x, p3y) = p3
+
+    p1x * (p2y - p3y) +
+    p2x * (p3y - p1y) +
+    p3x * (p1y - p2y)
+
+let CheckTriWinding allowReversed t =
+    let detTri = Det2D t
+    if detTri < 0.0 then
+        if allowReversed then
+            let (p1, p2, p3) = t
+            (p1, p3, p2)
+        else
+            raise (Exception "Triangle has wrong winding direction")
+    else
+        t
+
+let boundaryCollideChk eps t =
+    (Det2D t) < eps
+
+let boundaryDoesntCollideChk eps t =
+    (Det2D t) <= eps
+
+let TriTri2D eps allowReversed onBoundary t1 t2 =
+    // Triangles must be expressed anti-clockwise
+    let t3 = CheckTriWinding allowReversed t1
+    let t4 = CheckTriWinding allowReversed t2
+
+    // 'onBoundary' determines whether points on boundary are considered as colliding or not
+    let chkEdge = if onBoundary then boundaryCollideChk else boundaryDoesntCollideChk
+    let (t1p1, t1p2, t1p3) = t3
+    let (t2p1, t2p2, t2p3) = t4
+
+    // Check all points of t2 lay on the external side of edge E.
+    // If they do, the triangles do not overlap.
+    if (chkEdge eps (t1p1, t1p2, t2p1)) && (chkEdge eps (t1p1, t1p2, t2p2)) && (chkEdge eps (t1p1, t1p2, t2p3)) then
+        false
+    else if (chkEdge eps (t1p2, t1p3, t2p1)) && (chkEdge eps (t1p2, t1p3, t2p2)) && (chkEdge eps (t1p2, t1p3, t2p3)) then
+        false
+    else if (chkEdge eps (t1p3, t1p1, t2p1)) && (chkEdge eps (t1p3, t1p1, t2p2)) && (chkEdge eps (t1p3, t1p1, t2p3)) then
+        false
+
+    // Check all points of t1 lay on the external side of edge E.
+    // If they do, the triangles do not overlap.
+    else if (chkEdge eps (t2p1, t2p2, t1p1)) && (chkEdge eps (t2p1, t2p2, t1p2)) && (chkEdge eps (t2p1, t2p2, t1p3)) then
+        false
+    else if (chkEdge eps (t2p2, t2p3, t1p1)) && (chkEdge eps (t2p2, t2p3, t1p2)) && (chkEdge eps (t2p2, t2p3, t1p3)) then
+        false
+    else if (chkEdge eps (t2p3, t2p1, t1p1)) && (chkEdge eps (t2p3, t2p1, t1p2)) && (chkEdge eps (t2p3, t2p1, t1p3)) then
+        false
+
+    else
+        // The triangles overlap
+        true
+
+let Print t1 t2 =
+    Console.WriteLine("{0} and\n{1}\n{2}\n", t1, t2, if TriTri2D 0.0 false true t1 t2 then "overlap" else "do not overlap")
+
+[<EntryPoint>]
+let main _ =
+    let t1 = ((0.0, 0.0), (5.0, 0.0), (0.0, 5.0))
+    let t2 = ((0.0, 0.0), (5.0, 0.0), (0.0, 6.0))
+    Print t1 t2
+
+    let t3 = ((0.0, 0.0), (0.0, 5.0), (5.0, 0.0))
+    Console.WriteLine("{0} and\n{1}\n{2}\n", t3, t3, if TriTri2D 0.0 true true t3 t3 then "overlap (reversed)" else "do not overlap")
+
+    let t4 = ((0.0, 0.0), (5.0, 0.0), (0.0, 5.0))
+    let t5 = ((-10.0, 0.0), (-5.0, 0.0), (-1.0, 6.0))
+    Print t4 t5
+
+    let t6 = ((0.0, 0.0), (5.0, 0.0), (2.5, 5.0))
+    let t7 = ((0.0, 4.0), (2.5, -1.0), (5.0, 4.0))
+    Print t6 t7
+
+    let t8 = ((0.0, 0.0), (1.0, 1.0), (0.0, 2.0))
+    let t9 = ((2.0, 1.0), (3.0, 0.0), (3.0, 2.0))
+    Print t8 t9
+
+    let t10 = ((2.0, 1.0), (3.0, -2.0), (3.0, 4.0))
+    Print t8 t10
+
+    let t11 = ((0.0, 0.0), (1.0, 0.0), (0.0, 1.0))
+    let t12 = ((1.0, 0.0), (2.0, 0.0), (1.0, 1.1))
+    printfn "The following triangles which have only a single corner in contact, if boundary points collide"
+    Print t11 t12
+
+    Console.WriteLine("{0} and\n{1}\nwhich have only a single corner in contact, if boundary points do not collide\n{2}", t11, t12, if TriTri2D 0.0 false false t11 t12 then "overlap" else "do not overlap")
+
+    0 // return an integer exit code