"""Simple collision check.
This module provides simple collision checking appropriate for
-shmups. It provides a routine to check whether two moving circles
+shmups. It provides routines to check whether two moving circles
collided during the past frame.
+An equivalent C-based version will be used automatically if it was
+compiled and installed with the module. If available, it will be noted
+in the docstrings for the functions.
+
Basic Usage:
from bulletml.collision import collides
Usually, you'll want to use the 'collides' method instead, but
this one can be useful for just checking to see if the player has
entered an area or hit a stationary oject.
+
+ (This function is unoptimized.)
"""
dx = a.x - b.x
dy = a.y - b.y
- radius = getattr(a, 'radius', 0.5) + getattr(b, 'radius', 0.5)
+ try:
+ radius = a.radius + b.radius
+ except AttributeError:
+ radius = getattr(a, 'radius', 0.5) + getattr(b, 'radius', 0.5)
return dx * dx + dy * dy <= radius * radius
px, py - not required, defaults to x, y, previous frame position
radius - not required, defaults to 0.5
+ (This function is unoptimized.)
+
"""
# Current locations.
xa = a.x
yb = b.y
# Treat b as a point, we only need one radius.
- radius = getattr(a, 'radius', 0.5) + getattr(b, 'radius', 0.5)
+ try:
+ radius = a.radius + b.radius
+ except AttributeError:
+ radius = getattr(a, 'radius', 0.5) + getattr(b, 'radius', 0.5)
# Previous frame locations.
- pxa = getattr(a, 'px', xa)
- pya = getattr(a, 'py', ya)
- pxb = getattr(b, 'px', xb)
- pyb = getattr(b, 'py', yb)
+ try: pxa = a.px
+ except KeyError: pxa = xa
+ try: pya = a.py
+ except KeyError: pya = ya
+ try: pxb = b.px
+ except KeyError: pxb = xb
+ try: pyb = b.py
+ except KeyError: pyb = yb
# Translate b's final position to be relative to a's start.
# And now, circle/line collision.
dir_x = pxa + (xb - xa) - pxb
dir_y = pya + (yb - ya) - pyb
- if abs(dir_x) < 0.0001 and abs(dir_y) < 0.0001:
- # b did not move relative to a, so do point/circle.
- dx = pxb - pxa
- dy = pyb - pya
- return dx * dx + dy * dy < radius * radius
-
diff_x = pxa - pxb
diff_y = pya - pyb
+ if (dir_x < 0.0001 and dir_x > -0.0001
+ and dir_y < 0.0001 and dir_y > -0.0001):
+ # b did not move relative to a, so do point/circle.
+ return diff_x * diff_x + diff_y * diff_y < radius * radius
# dot(diff, dir) / dot(dir, dir)
t = (diff_x * dir_x + diff_y * dir_y) / (dir_x * dir_x + dir_y * dir_y)
# dist_sq < radius_sq
return dist_x * dist_x + dist_y * dist_y <= radius * radius
+
+def collides_all(a, others):
+ """Filter the second argument to those that collide with the first.
+
+ This is equivalent to filter(lambda o: collides(a, o), others),
+ but is much faster when the compiled extension is available (which
+ it is not currently).
+
+ """
+ return filter(lambda o: collides(a, o), others)
+
+try:
+ from bulletml._collision import collides, overlaps, collides_all
+except ImportError:
+ pass