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comparison orpg/mapper/map_utils.py @ 0:4385a7d0efd1 grumpy-goblin

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Deleted and repushed it with the 'grumpy-goblin' branch. I forgot a y
author sirebral
date Tue, 14 Jul 2009 16:41:58 -0500
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children 072ffc1d466f
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-1:000000000000 0:4385a7d0efd1
1 #------------------------------------------------
2 # file: map_utils.py
3 #
4 # This file contains generic utility functions
5 # for use in the openrpg mapping system
6 # -----------------------------------------------
7
8 import math
9
10 #-----------------------------------------------------------------------
11 # distance_between()
12 # Returns the distance between two points
13 #-----------------------------------------------------------------------
14 def distance_between( x1, y1, x2, y2 ):
15 "Returns the distance between two points"
16 dx = x2 - x1
17 dy = y2 - y1
18 return math.sqrt( dx*dx + dy*dy )
19
20 #-----------------------------------------------------------------------
21 # proximity_test()
22 # Tests if 'test_point' (T) is close (within 'threshold' units) to the
23 # line segment 'start_point' to 'end_point' (PQ).
24 #
25 # The closest point (R) to T on the line PQ is given by:
26 # R = P + u (Q - P)
27 # TR is perpendicular to PQ so:
28 # (T - R) dot (Q - P) = 0
29 # Solving these two equations gives the equation for u (see below).
30 #
31 # If u < 0 or u > 1 then R is not within the line segment and we simply
32 # test against point P or Q.
33 #-----------------------------------------------------------------------
34 def proximity_test( start_point, end_point, test_point, threshold ):
35 "Test if a point is close to a line segment"
36 x1,y1 = start_point
37 x2,y2 = end_point
38 xt,yt = test_point
39 x1 = float(x1)
40 x2 = float(x2)
41 y1 = float(y1)
42 y2 = float(y2)
43 xt = float(xt)
44 yt = float(yt)
45
46 # Coincident points?
47 if x1 == x2 and y1 == y2:
48 d = distance_between(xt, yt, x1, y1)
49 else:
50 dx = x2 - x1
51 dy = y2 - y1
52 u = ((xt - x1) * dx + (yt - y1) * dy) / (dx*dx + dy*dy)
53 if u < 0:
54 d = distance_between(xt, yt, x1, y1)
55 elif u > 1:
56 d = distance_between(xt, yt, x2, y2)
57 else:
58 xr = x1 + u * dx
59 yr = y1 + u * dy
60 d = distance_between(xt, yt, xr, yr)
61 return d <= threshold