def step(self, dt):
""" Computes one game step or tick, dt being the
approx time elapsed since the previous tick """
black = (0, 0, 0)
self.screen.fill(black)
# Handle body drag creation
self.input.update()
if self.input.body:
body = self.input.body
clickP = self.input.clickPosition
pg.draw.line(self.screen, pg.Color(255,255,255,255),
(clickP.x, clickP.y), (body.position.x, body.position.y), 1)
self.drawCircle(self.screen, self.screenToWorld(body.position),
pg.Color(255,255,255,255), body.radius)
lockedPhysicsList = [] # Used for dynamic calculations and collisions
# Iterate over tree, update and draw
for body in self.rootBody:
body.update(dt)
bodyPos = body.getWorldPosition()
self.drawCircle(self.screen, bodyPos, body.color, body.radius)
lockedPhysicsList.append(body)
# Update and draw all dynamic bodies
for index, body in enumerate(self.dynamicBodies):
body.update(lockedPhysicsList, dt)
self.drawCircle(self.screen, (body.position),
pg.Color(255,255,255,255), body.radius)
if Vec2D.magnitudeSquared(body.position) > 1000000 or body.hasCollided(): # Out of game area
del self.dynamicBodies[index]
pg.display.flip()
def update(self, lockedBodies, dt):
""" Updates velocity and applies to position based on all
the locked bodies in the system """
for body in lockedBodies:
rawDisplace = body.getWorldPosition() - self.position
direction = Vec2D.normalize(rawDisplace)
displacementSquared = Vec2D.magnitudeSquared(rawDisplace)
acceleration = dt * self.gConstant * body.mass / max(
10, displacementSquared
) # min radius 10 to prevent crazy acceleration
self.velocity = self.velocity + Vec2D.scale(
direction, acceleration)
self.position = self.position + self.velocity
# Have we collided
if not self.collided:
actualDisplacement = math.sqrt(displacementSquared)
if actualDisplacement < (self.radius + body.radius):
self.collided = True # Collision has occured
