1 """Simple collision check.
3 This module provides simple collision checking appropriate for
4 shmups. It provides a routine to check whether two moving circles
5 collided during the past frame.
7 If Pyrex was available when installing, this will used optimized
8 versions of the functions.
12 from bulletml.collision import collides
14 for bullet in bullets:
15 if collides(player, bullet): ... # Kill the player.
18 from __future__
import division
21 """Return true if two circles are overlapping.
23 Usually, you'll want to use the 'collides' method instead, but
24 this one can be useful for just checking to see if the player has
25 entered an area or hit a stationary oject.
27 (This function is unoptimized.)
32 radius
= getattr(a
, 'radius', 0.5) + getattr(b
, 'radius', 0.5)
34 return dx
* dx
+ dy
* dy
<= radius
* radius
37 """Return true if the two moving circles collide.
39 a and b should have the following attributes:
41 x, y - required, current position
42 px, py - not required, defaults to x, y, previous frame position
43 radius - not required, defaults to 0.5
45 (This function is unoptimized.)
54 # Treat b as a point, we only need one radius.
55 radius
= getattr(a
, 'radius', 0.5) + getattr(b
, 'radius', 0.5)
57 # Previous frame locations.
58 pxa
= getattr(a
, 'px', xa
)
59 pya
= getattr(a
, 'py', ya
)
60 pxb
= getattr(b
, 'px', xb
)
61 pyb
= getattr(b
, 'py', yb
)
63 # Translate b's final position to be relative to a's start.
64 # And now, circle/line collision.
65 dir_x
= pxa
+ (xb
- xa
) - pxb
66 dir_y
= pya
+ (yb
- ya
) - pyb
68 if abs(dir_x
) < 0.0001 and abs(dir_y
) < 0.0001:
69 # b did not move relative to a, so do point/circle.
72 return dx
* dx
+ dy
* dy
< radius
* radius
77 # dot(diff, dir) / dot(dir, dir)
78 t
= (diff_x
* dir_x
+ diff_y
* dir_y
) / (dir_x
* dir_x
+ dir_y
* dir_y
)
84 dist_x
= pxa
- (pxb
+ dir_x
* t
)
85 dist_y
= pya
- (pyb
+ dir_y
* t
)
88 return dist_x
* dist_x
+ dist_y
* dist_y
<= radius
* radius
90 def collides_all(a
, others
):
91 """Filter the second argument to those that collide with the first.
93 This is equivalent to filter(lambda o: collides(a, o), others),
94 but is much faster when the compiled extension is available (which
98 return filter(lambda o
: collides(a
, o
), others
)
101 from bulletml
._collision
import collides
, overlaps
, collides_all