Data commit

Task/Determine-if-two-triangles-overlap/FreeBASIC/determine-if-two-triangles-overlap.basic

@@ -0,0 +1,93 @@
+#macro min(x,y)
+   Iif(x>y,y,x)
+#endmacro
+#macro max(x,y)
+   Iif(x>y,x,y)
+#endmacro
+
+type pnt  'typedef for a point
+    x as double
+    y as double
+end type
+
+type edg  'typedef for an edge
+    p1 as pnt
+    p2 as pnt
+end type
+
+function point_in_tri( r as pnt, a as pnt, b as pnt, c as pnt ) as boolean
+    'uses barycentric coordinates to determine whether point r is in the triangle defined by a, b, c
+    dim as double k = ((b.y - c.y)*(a.x - c.x) + (c.x - b.x)*(a.y - c.y))
+    dim as double v = ((b.y - c.y)*(r.x - c.x) + (c.x - b.x)*(r.y - c.y)) / k
+    dim as double w = ((c.y - a.y)*(r.x - c.x) + (a.x - c.x)*(r.y - c.y)) / k
+    dim as double z = 1 - v- w
+    if v<0 or v>1 then return false
+    if w<0 or w>1 then return false
+    if z<0 or z>1 then return false
+    return true
+end function
+
+function bbox_overlap( a1 as pnt, a2 as pnt, b1 as pnt, b2 as pnt) as boolean
+    dim as double a1x = min(a1.x, a2.x), a1y = min(a1.y, a2.y)
+    dim as double a2x = max(a1.x, a2.x), a2y = max(a1.y, a2.y)
+    dim as double b1x = min(b1.x, b2.x), b1y = min(b1.y, b2.y)
+    dim as double b2x = max(b1.x, b2.x), b2y = max(b1.y, b2.y)
+    if a1x > b2x or b1x > a2x then return false
+    if a1y > b2y or b2y > a2y then return false
+    return true
+end function
+
+function ccw( a as pnt, b as pnt, c as pnt) as double
+   return (b.x - a.x) * (c.y - a.y) - (c.x - a.x) * (b.y - a.y)
+end function
+
+function line_intersect( a as edg, b as edg ) as boolean
+   if ccw(a.p1, a.p2, b.p1)*ccw(a.p1, a.p2, b.p2) > 0 then return false
+   if ccw(b.p1, b.p2, a.p1)*ccw(b.p1, b.p2, a.p2) > 0 then return false
+   if not bbox_overlap( a.p1, a.p2, b.p1, b.p2 ) then return false
+   return true
+end function
+
+function triangle_overlap( a() as pnt, b() as pnt ) as boolean
+    'if two triangles overlap then either a corner of one triangle is inside
+    'the other OR an edge of one triangle intersects an edge of the other.
+    dim as uinteger i, j
+    dim as edg c, d
+    for i = 0 to 2
+        if point_in_tri( a(i), b(0), b(1), b(2) ) then return true
+        if point_in_tri( b(i), a(0), a(1), a(2) ) then return true
+        c.p1.x = a(i).x
+        c.p1.y = a(i).y
+        c.p2.x = a((i+1) mod 3).x
+        c.p2.y = a((i+1) mod 3).y
+        for j = 0 to 2
+            d.p1.x = b(i).x
+            d.p1.y = b(i).y
+            d.p2.x = b((i+1) mod 3).x
+            d.p2.y = b((i+1) mod 3).y
+            if line_intersect( c, d ) then return true
+        next j
+    next i
+    return 00
+end function
+
+data 0,0 , 5,0 , 0,5     ,    0,0 , 5,0 , 0,6
+data 0,0 , 0,5 , 5,0     ,    0,0 , 0,5 , 5,0
+data 0,0 , 5,0 , 0,5     ,    -10,0 , -5,0 , -1,6
+data 0,0 , 5,0 , 2.5,5   ,    0,4 , 2.5,-1 , 5,4
+data 0,0 , 1,1 , 0,2     ,    2,1 , 3,0 , 3,2
+data 0,0 , 1,1 , 0,2     ,    2,1 , 3,-2 , 3,4
+data 0,0 , 1,0 , 0,1     ,    1,0 , 2,0 , 1,1
+
+dim as uinteger t, i
+dim as pnt a(0 to 2), b(0 to 2)
+
+for t = 1 to 7
+    for i = 0 to 2
+        read a(i).x, a(i).y
+    next i
+    for i = 0 to 2
+        read b(i).x, b(i).y
+    next i
+    print triangle_overlap( a(), b() )
+next t