def turning_radius(self):
''' Returns the radius of the circle needed to ride over the target
'''
if not self.target.visible: return 1e12
(a0, b0) = (self.target.x - self.x, self.target.y - self.y)
#mag: distance between Bike and it's target
mag = hypot(a0, b0)
#psi: angle of target relative to Bike's path of travel
psi = util.normangle(atan2(b0, a0) - self.angle)
self.psi_sign = 1 if psi > 0 else -1
if fabs(psi) > pi / 2.0:
# The player is looking at a point over his shoulder
tmp = fabs(mag * sin(psi - self.psi_sign * pi/2.0))
self.target.x += tmp * cos(self.angle)
self.target.y += tmp * sin(self.angle)
psi = self.psi_sign * pi/2.0
# calculate as though the target is parallel with path of travel at
# 90deg angle to the path of travel
a0 = self.target.x - self.x
b0 = self.target.y - self.y
mag = hypot(a0, b0)
a = mag * sin(psi)
b = mag * cos(psi)
if fabs(a) > 1e-12:
return fabs((a*a + b*b) / (2.0*a))
else:
return 1e12
def update(self):
r = self.turning_radius()
r_min = self.mass * self.speed * self.speed / self.ft
v_max = sqrt(r * self.ft / self.mass)
dts = self.dt * 60.0 / 1000.0
# clear the drawing callbacks
self.draw_cb = []
if r < r_min and self.target.visible:
# Must brake in order to turn
self.speed = max((1e-12, self.speed - self.brake * dts))
r = 1e12
# Draw the predicted braking vector
brake_dist = (0.5 * ((self.speed - v_max) / self.brake) *
(self.speed + v_max))
@self.draw_cb.append
def drawme(screen):
start = self.x, self.y
end = (self.x + cos(self.angle) * brake_dist,
self.y + sin(self.angle) * brake_dist)
pygame.draw.line(screen, (127,0,0), start, end, 10)
else:
# Can turn without breaking
if not self.target.visible:
v_max = 1e12
# Important to keep v_max * 0.98 because otherwise, the bike is
# really close to over accelerating with random fluctuations This
# is a little messy, but i think i understand the behavior if not
# the best solution.
self.speed = min((self.speed + self.accel * dts,
self.max_speed, v_max * 0.98))
l = self.speed * dts
if self.target.visible and fabs(r) < 1e9:
# phi: angle of rotation to travel distance l over circle with
# radius r
phi = l / r
self.angle = util.normangle(self.angle + (phi * self.psi_sign))
# c: the chord with angle phi through circle with radius r.
# extremely close to l for small values of l
c = 2.0 * r * sin(phi/2.0)
# fabs(c-l) is typically less than 1e-5 pixels
self.x += c * cos(phi+self.angle)
self.y += c * sin(phi+self.angle)
# the remainder of this block is debug
# find the center of the turning circle
tmp = self.angle + (self.psi_sign * pi/2.0)
debugx = int(self.x + r * cos(tmp))
debugy = int(self.y + r * sin(tmp))
# the turning circle
if(r < 1000 and r > 0):
@self.draw_cb.append
def drawme(s):
pygame.draw.circle(s, (0,0,0), (debugx, debugy), int(r), 1)
pygame.draw.circle(s, (0,0,0), (debugx, debugy), 2, 0)
# The vector of travel, tangent to the turning circle
@self.draw_cb.append
def drawme(s):
dest = (self.x + cos(self.angle) * 100,
self.y + sin(self.angle) * 100)
pygame.draw.line(s, (0,0,0), self.rect.center, dest, 1)
else:
self.x += l * cos(self.angle)
self.y += l * sin(self.angle)
# the rect uses ints, so it's just for drawing
self.rect.center = (self.x, self.y)
# rotate and recenter. the centering is magic :(
self.image = pygame.transform.rotate(self.original,
-degrees(self.angle))
self.rect = self.image.get_rect(center=self.rect.center)
if self.target.rect.collidepoint(self.rect.center):
self.target.unplace()
