Data commit

Task/Ray-casting-algorithm/Python/ray-casting-algorithm-1.py

@@ -0,0 +1,102 @@
+from collections import namedtuple
+from pprint import pprint as pp
+import sys
+
+Pt = namedtuple('Pt', 'x, y')               # Point
+Edge = namedtuple('Edge', 'a, b')           # Polygon edge from a to b
+Poly = namedtuple('Poly', 'name, edges')    # Polygon
+
+_eps = 0.00001
+_huge = sys.float_info.max
+_tiny = sys.float_info.min
+
+def rayintersectseg(p, edge):
+    ''' takes a point p=Pt() and an edge of two endpoints a,b=Pt() of a line segment returns boolean
+    '''
+    a,b = edge
+    if a.y > b.y:
+        a,b = b,a
+    if p.y == a.y or p.y == b.y:
+        p = Pt(p.x, p.y + _eps)
+
+    intersect = False
+
+    if (p.y > b.y or p.y < a.y) or (
+        p.x > max(a.x, b.x)):
+        return False
+
+    if p.x < min(a.x, b.x):
+        intersect = True
+    else:
+        if abs(a.x - b.x) > _tiny:
+            m_red = (b.y - a.y) / float(b.x - a.x)
+        else:
+            m_red = _huge
+        if abs(a.x - p.x) > _tiny:
+            m_blue = (p.y - a.y) / float(p.x - a.x)
+        else:
+            m_blue = _huge
+        intersect = m_blue >= m_red
+    return intersect
+
+def _odd(x): return x%2 == 1
+
+def ispointinside(p, poly):
+    ln = len(poly)
+    return _odd(sum(rayintersectseg(p, edge)
+                    for edge in poly.edges ))
+
+def polypp(poly):
+    print ("\n  Polygon(name='%s', edges=(" % poly.name)
+    print ('   ', ',\n    '.join(str(e) for e in poly.edges) + '\n    ))')
+
+if __name__ == '__main__':
+    polys = [
+      Poly(name='square', edges=(
+        Edge(a=Pt(x=0, y=0), b=Pt(x=10, y=0)),
+        Edge(a=Pt(x=10, y=0), b=Pt(x=10, y=10)),
+        Edge(a=Pt(x=10, y=10), b=Pt(x=0, y=10)),
+        Edge(a=Pt(x=0, y=10), b=Pt(x=0, y=0))
+        )),
+      Poly(name='square_hole', edges=(
+        Edge(a=Pt(x=0, y=0), b=Pt(x=10, y=0)),
+        Edge(a=Pt(x=10, y=0), b=Pt(x=10, y=10)),
+        Edge(a=Pt(x=10, y=10), b=Pt(x=0, y=10)),
+        Edge(a=Pt(x=0, y=10), b=Pt(x=0, y=0)),
+        Edge(a=Pt(x=2.5, y=2.5), b=Pt(x=7.5, y=2.5)),
+        Edge(a=Pt(x=7.5, y=2.5), b=Pt(x=7.5, y=7.5)),
+        Edge(a=Pt(x=7.5, y=7.5), b=Pt(x=2.5, y=7.5)),
+        Edge(a=Pt(x=2.5, y=7.5), b=Pt(x=2.5, y=2.5))
+        )),
+      Poly(name='strange', edges=(
+        Edge(a=Pt(x=0, y=0), b=Pt(x=2.5, y=2.5)),
+        Edge(a=Pt(x=2.5, y=2.5), b=Pt(x=0, y=10)),
+        Edge(a=Pt(x=0, y=10), b=Pt(x=2.5, y=7.5)),
+        Edge(a=Pt(x=2.5, y=7.5), b=Pt(x=7.5, y=7.5)),
+        Edge(a=Pt(x=7.5, y=7.5), b=Pt(x=10, y=10)),
+        Edge(a=Pt(x=10, y=10), b=Pt(x=10, y=0)),
+        Edge(a=Pt(x=10, y=0), b=Pt(x=2.5, y=2.5))
+        )),
+      Poly(name='exagon', edges=(
+        Edge(a=Pt(x=3, y=0), b=Pt(x=7, y=0)),
+        Edge(a=Pt(x=7, y=0), b=Pt(x=10, y=5)),
+        Edge(a=Pt(x=10, y=5), b=Pt(x=7, y=10)),
+        Edge(a=Pt(x=7, y=10), b=Pt(x=3, y=10)),
+        Edge(a=Pt(x=3, y=10), b=Pt(x=0, y=5)),
+        Edge(a=Pt(x=0, y=5), b=Pt(x=3, y=0))
+        )),
+      ]
+    testpoints = (Pt(x=5, y=5), Pt(x=5, y=8),
+                  Pt(x=-10, y=5), Pt(x=0, y=5),
+                  Pt(x=10, y=5), Pt(x=8, y=5),
+                  Pt(x=10, y=10))
+
+    print ("\n TESTING WHETHER POINTS ARE WITHIN POLYGONS")
+    for poly in polys:
+        polypp(poly)
+        print ('   ', '\t'.join("%s: %s" % (p, ispointinside(p, poly))
+                               for p in testpoints[:3]))
+        print ('   ', '\t'.join("%s: %s" % (p, ispointinside(p, poly))
+                               for p in testpoints[3:6]))
+        print ('   ', '\t'.join("%s: %s" % (p, ispointinside(p, poly))
+                               for p in testpoints[6:]))