1 """Simple collision check.
3 This module provides simple collision checking appropriate for
4 shmups. It provides routines to check whether two moving circles
5 collided during the past frame.
7 An equivalent C-based version will be used automatically if it was
8 compiled and installed with the module. If available, it will be noted
9 in the docstrings for the functions.
13 from bulletml.collision import collides
15 for bullet in bullets:
16 if collides(player, bullet): ... # Kill the player.
19 from __future__
import division
22 """Return true if two circles are overlapping.
24 Usually, you'll want to use the 'collides' method instead, but
25 this one can be useful for just checking to see if the player has
26 entered an area or hit a stationary oject.
28 (This function is unoptimized.)
34 radius
= a
.radius
+ b
.radius
35 except AttributeError:
36 radius
= getattr(a
, 'radius', 0.5) + getattr(b
, 'radius', 0.5)
38 return dx
* dx
+ dy
* dy
<= radius
* radius
41 """Return true if the two moving circles collide.
43 a and b should have the following attributes:
45 x, y - required, current position
46 px, py - not required, defaults to x, y, previous frame position
47 radius - not required, defaults to 0.5
49 (This function is unoptimized.)
58 # Treat b as a point, we only need one radius.
60 radius
= a
.radius
+ b
.radius
61 except AttributeError:
62 radius
= getattr(a
, 'radius', 0.5) + getattr(b
, 'radius', 0.5)
64 # Previous frame locations.
66 except KeyError: pxa
= xa
68 except KeyError: pya
= ya
70 except KeyError: pxb
= xb
72 except KeyError: pyb
= yb
74 # Translate b's final position to be relative to a's start.
75 # And now, circle/line collision.
76 dir_x
= pxa
+ (xb
- xa
) - pxb
77 dir_y
= pya
+ (yb
- ya
) - pyb
81 if (dir_x
< 0.0001 and dir_x
> -0.0001
82 and dir_y
< 0.0001 and dir_y
> -0.0001):
83 # b did not move relative to a, so do point/circle.
84 return diff_x
* diff_x
+ diff_y
* diff_y
< radius
* radius
86 # dot(diff, dir) / dot(dir, dir)
87 t
= (diff_x
* dir_x
+ diff_y
* dir_y
) / (dir_x
* dir_x
+ dir_y
* dir_y
)
93 dist_x
= pxa
- (pxb
+ dir_x
* t
)
94 dist_y
= pya
- (pyb
+ dir_y
* t
)
97 return dist_x
* dist_x
+ dist_y
* dist_y
<= radius
* radius
99 def collides_all(a
, others
):
100 """Filter the second argument to those that collide with the first.
102 This is equivalent to filter(lambda o: collides(a, o), others),
103 but is much faster when the compiled extension is available (which
104 it is not currently).
107 return filter(lambda o
: collides(a
, o
), others
)
110 from bulletml
._collision
import collides
, overlaps
, collides_all