Python实现我的世界小游戏源代码

  from __future__ import division

  import sys

  import math

  import random

  import time

  from collections import deque

  from pyglet import image

  from pyglet.gl import *

  from pyglet.graphics import TextureGroup

  from pyglet.window import key, mouse

  TICKS_PER_SEC = 60

  # Size of sectors used to ease block loading.

  SECTOR_SIZE = 16

  WALKING_SPEED = 5

  FLYING_SPEED = 15

  GRAVITY = 20.0

  MAX_JUMP_HEIGHT = 1.0 # About the height of a block.

  # To derive the formula for calculating jump speed, first solve

  # v_t = v_0 + a * t

  # for the time at which you achieve maximum height, where a is the acceleration

  # due to gravity and v_t = 0. This gives:

  # t = - v_0 / a

  # Use t and the desired MAX_JUMP_HEIGHT to solve for v_0 (jump speed) in

  # s = s_0 + v_0 * t + (a * t^2) / 2

  JUMP_SPEED = math.sqrt(2 * GRAVITY * MAX_JUMP_HEIGHT)

  TERMINAL_VELOCITY = 50

  PLAYER_HEIGHT = 2

  if sys.version_info[0] >= 3:

  xrange = range

  def cube_vertices(x, y, z, n):

  """ Return the vertices of the cube at position x, y, z with size 2*n.

  """

  return [

  x-n,y+n,z-n, x-n,y+n,z+n, x+n,y+n,z+n, x+n,y+n,z-n, # top

  x-n,y-n,z-n, x+n,y-n,z-n, x+n,y-n,z+n, x-n,y-n,z+n, # bottom

  x-n,y-n,z-n, x-n,y-n,z+n, x-n,y+n,z+n, x-n,y+n,z-n, # left

  x+n,y-n,z+n, x+n,y-n,z-n, x+n,y+n,z-n, x+n,y+n,z+n, # right

  x-n,y-n,z+n, x+n,y-n,z+n, x+n,y+n,z+n, x-n,y+n,z+n, # front

  x+n,y-n,z-n, x-n,y-n,z-n, x-n,y+n,z-n, x+n,y+n,z-n, # back

  ]

  def tex_coord(x, y, n=4):

  """ Return the bounding vertices of the texture square.

  """

  m = 1.0 / n

  dx = x * m

  dy = y * m

  return dx, dy, dx + m, dy, dx + m, dy + m, dx, dy + m

  def tex_coords(top, bottom, side):

  """ Return a list of the texture squares for the top, bottom and side.

  """

  top = tex_coord(*top)

  bottom = tex_coord(*bottom)

  side = tex_coord(*side)

  result = []

  result.extend(top)

  result.extend(bottom)

  result.extend(side * 4)

  return result

  TEXTURE_PATH = 'texture.png'

  GRASS = tex_coords((1, 0), (0, 1), (0, 0))

  SAND = tex_coords((1, 1), (1, 1), (1, 1))

  BRICK = tex_coords((2, 0), (2, 0), (2, 0))

  STONE = tex_coords((2, 1), (2, 1), (2, 1))

  FACES = [

  ( 0, 1, 0),

  ( 0,-1, 0),

  (-1, 0, 0),

  ( 1, 0, 0),

  ( 0, 0, 1),

  ( 0, 0,-1),

  ]

  def normalize(position):

  """ Accepts `position` of arbitrary precision and returns the block

  containing that position.

  Parameters

  ----------

  position : tuple of len 3

  Returns

  -------

  block_position : tuple of ints of len 3

  """

  x, y, z = position

  x, y, z = (int(round(x)), int(round(y)), int(round(z)))

  return (x, y, z)

  def sectorize(position):

  """ Returns a tuple representing the sector for the given `position`.

  Parameters

  ----------

  position : tuple of len 3

  Returns

  -------

  sector : tuple of len 3

  """

  x, y, z = normalize(position)

  x, y, z = x // SECTOR_SIZE, y // SECTOR_SIZE, z // SECTOR_SIZE

  return (x, 0, z)

  class Model(object):

  def __init__(self):

  # A Batch is a collection of vertex lists for batched rendering.

  self.batch = pyglet.graphics.Batch()

  # A TextureGroup manages an OpenGL texture.

  self.group = TextureGroup(image.load(TEXTURE_PATH).get_texture())

  # A mapping from position to the texture of the block at that position.

  # This defines all the blocks that are currently in the world.

  self.world = {}

  # Same mapping as `world` but only contains blocks that are shown.

  self.shown = {}

  # Mapping from position to a pyglet `VertextList` for all shown blocks.

  self._shown = {}

  # Mapping from sector to a list of positions inside that sector.

  self.sectors = {}

  # Simple function queue implementation. The queue is populated with

  # _show_block() and _hide_block() calls

  self.queue = deque()

  self._initialize()

  def _initialize(self):

  """ Initialize the world by placing all the blocks.

  """

  n = 80 # 1/2 width and height of world

  s = 1 # step size

  y = 0 # initial y height

  for x in xrange(-n, n + 1, s):

  for z in xrange(-n, n + 1, s):

  # create a layer stone an grass everywhere.

  self.add_block((x, y - 2, z), GRASS, immediate=False)

  self.add_block((x, y - 3, z), STONE, immediate=False)

  if x in (-n, n) or z in (-n, n):

  # create outer walls.

  for dy in xrange(-2, 3):

  self.add_block((x, y + dy, z), STONE, immediate=False)

  # generate the hills randomly

  o = n - 10

  for _ in xrange(120):

  a = random.randint(-o, o) # x position of the hill

  b = random.randint(-o, o) # z position of the hill

  c = -1 # base of the hill

  h = random.randint(1, 6) # height of the hill

  s = random.randint(4, 8) # 2 * s is the side length of the hill

  d = 1 # how quickly to taper off the hills

  t = random.choice([GRASS, SAND, BRICK])

  for y in xrange(c, c + h):

  for x in xrange(a - s, a + s + 1):

  for z in xrange(b - s, b + s + 1):

  if (x - a) ** 2 + (z - b) ** 2 > (s + 1) ** 2:

  continue

  if (x - 0) ** 2 + (z - 0) ** 2 < 5 ** 2:

  continue

  self.add_block((x, y, z), t, immediate=False)

  s -= d # decrement side lenth so hills taper off

  def hit_test(self, position, vector, max_distance=8):

  """ Line of sight search from current position. If a block is

  intersected it is returned, along with the block previously in the line

  of sight. If no block is found, return None, None.

  Parameters

  ----------

  position : tuple of len 3

  The (x, y, z) position to check visibility from.

  vector : tuple of len 3

  The line of sight vector.

  max_distance : int

  How many blocks away to search for a hit.

  """

  m = 8

  x, y, z = position

  dx, dy, dz = vector

  previous = None

  for _ in xrange(max_distance * m):

  key = normalize((x, y, z))

  if key != previous and key in self.world:

  return key, previous

  previous = key

  x, y, z = x + dx / m, y + dy / m, z + dz / m

  return None, None

  def exposed(self, position):

  """ Returns False is given `position` is surrounded on all 6 sides by

  blocks, True otherwise.

  """

  x, y, z = position

  for dx, dy, dz in FACES:

  if (x + dx, y + dy, z + dz) not in self.world:

  return True

  return False

  def add_block(self, position, texture, immediate=True):

  """ Add a block with the given `texture` and `position` to the world.

  Parameters

  ----------

  position : tuple of len 3

  The (x, y, z) position of the block to add.

  texture : list of len 3

  The coordinates of the texture squares. Use `tex_coords()` to

  generate.

  immediate : bool

  Whether or not to draw the block immediately.

  """

  if position in self.world:

  self.remove_block(position, immediate)

  self.world[position] = texture

  self.sectors.setdefault(sectorize(position), []).append(position)

  if immediate:

  if self.exposed(position):

  self.show_block(position)

  self.check_neighbors(position)

  def remove_block(self, position, immediate=True):

  """ Remove the block at the given `position`.

  Parameters

  ----------

  position : tuple of len 3

  The (x, y, z) position of the block to remove.

  immediate : bool

  Whether or not to immediately remove block from canvas.

  """

  del self.world[position]

  self.sectors[sectorize(position)].remove(position)

  if immediate:

  if position in self.shown:

  self.hide_block(position)

  self.check_neighbors(position)

  def check_neighbors(self, position):

  """ Check all blocks surrounding `position` and ensure their visual

  state is current. This means hiding blocks that are not exposed and

  ensuring that all exposed blocks are shown. Usually used after a block

  is added or removed.

  """

  x, y, z = position

  for dx, dy, dz in FACES:

  key = (x + dx, y + dy, z + dz)

  if key not in self.world:

  continue

  if self.exposed(key):

  if key not in self.shown:

  self.show_block(key)

  else:

  if key in self.shown:

  self.hide_block(key)

  def show_block(self, position, immediate=True):

  """ Show the block at the given `position`. This method assumes the

  block has already been added with add_block()

  Parameters

  ----------

  position : tuple of len 3

  The (x, y, z) position of the block to show.

  immediate : bool

  Whether or not to show the block immediately.

  """

  texture = self.world[position]

  self.shown[position] = texture

  if immediate:

  self._show_block(position, texture)

  else:

  self._enqueue(self._show_block, position, texture)

  def _show_block(self, position, texture):

  """ Private implementation of the `show_block()` method.

  Parameters

  ----------

  position : tuple of len 3

  The (x, y, z) position of the block to show.

  texture : list of len 3

  The coordinates of the texture squares. Use `tex_coords()` to

  generate.

  """

  x, y, z = position

  vertex_data = cube_vertices(x, y, z, 0.5)

  texture_data = list(texture)

  # create vertex list

  # FIXME Maybe `add_indexed()` should be used instead

  self._shown[position] = self.batch.add(24, GL_QUADS, self.group,

  ('v3f/static', vertex_data),

  ('t2f/static', texture_data))

  def hide_block(self, position, immediate=True):

  """ Hide the block at the given `position`. Hiding does not remove the

  block from the world.

  Parameters

  ----------

  position : tuple of len 3

  The (x, y, z) position of the block to hide.

  immediate : bool

  Whether or not to immediately remove the block from the canvas.

  """

  self.shown.pop(position)

  if immediate:

  self._hide_block(position)

  else:

  self._enqueue(self._hide_block, position)

  def _hide_block(self, position):

  """ Private implementation of the 'hide_block()` method.

  """

  self._shown.pop(position).delete()

  def show_sector(self, sector):

  """ Ensure all blocks in the given sector that should be shown are

  drawn to the canvas.

  """

  for position in self.sectors.get(sector, []):

  if position not in self.shown and self.exposed(position):

  self.show_block(position, False)

  def hide_sector(self, sector):

  """ Ensure all blocks in the given sector that should be hidden are

  removed from the canvas.

  """

  for position in self.sectors.get(sector, []):

  if position in self.shown:

  self.hide_block(position, False)

  def change_sectors(self, before, after):

  """ Move from sector `before` to sector `after`. A sector is a

  contiguous x, y sub-region of world. Sectors are used to speed up

  world rendering.

  """

  before_set = set()

  after_set = set()

  pad = 4

  for dx in xrange(-pad, pad + 1):

  for dy in [0]: # xrange(-pad, pad + 1):

  for dz in xrange(-pad, pad + 1):

  if dx ** 2 + dy ** 2 + dz ** 2 > (pad + 1) ** 2:

  continue

  if before:

  x, y, z = before

  before_set.add((x + dx, y + dy, z + dz))

  if after:

  x, y, z = after

  after_set.add((x + dx, y + dy, z + dz))

  show = after_set - before_set

  hide = before_set - after_set

  for sector in show:

  self.show_sector(sector)

  for sector in hide:

  self.hide_sector(sector)

  def _enqueue(self, func, *args):

  """ Add `func` to the internal queue.

  """

  self.queue.append((func, args))

  def _dequeue(self):

  """ Pop the top function from the internal queue and call it.

  """

  func, args = self.queue.popleft()

  func(*args)

  def process_queue(self):

  """ Process the entire queue while taking periodic breaks. This allows

  the game loop to run smoothly. The queue contains calls to

  _show_block() and _hide_block() so this method should be called if

  add_block() or remove_block() was called with immediate=False

  """

  start = time.perf_counter()

  while self.queue and time.time()- start < 1.0 / TICKS_PER_SEC:

  self._dequeue()

  def process_entire_queue(self):

  """ Process the entire queue with no breaks.

  """

  while self.queue:

  self._dequeue()

  class Window(pyglet.window.Window):

  def __init__(self, *args, **kwargs):

  super(Window, self).__init__(*args, **kwargs)

  # Whether or not the window exclusively captures the mouse.

  self.exclusive = False

  # When flying gravity has no effect and speed is increased.

  self.flying = False

  # Strafing is moving lateral to the direction you are facing,

  # e.g. moving to the left or right while continuing to face forward.

  #

  # First element is -1 when moving forward, 1 when moving back, and 0

  # otherwise. The second element is -1 when moving left, 1 when moving

  # right, and 0 otherwise.

  self.strafe = [0, 0]

  # Current (x, y, z) position in the world, specified with floats. Note

  # that, perhaps unlike in math class, the y-axis is the vertical axis.

  self.position = (0, 0, 0)

  # First element is rotation of the player in the x-z plane (ground

  # plane) measured from the z-axis down. The second is the rotation

  # angle from the ground plane up. Rotation is in degrees.

  #

  # The vertical plane rotation ranges from -90 (looking straight down) to

  # 90 (looking straight up). The horizontal rotation range is unbounded.

  self.rotation = (0, 0)

  # Which sector the player is currently in.

  self.sector = None

  # The crosshairs at the center of the screen.

  self.reticle = None

  # Velocity in the y (upward) direction.

  self.dy = 0

  # A list of blocks the player can place. Hit num keys to cycle.

  self.inventory = [BRICK, GRASS, SAND]

  # The current block the user can place. Hit num keys to cycle.

  self.block = self.inventory[0]

  # Convenience list of num keys.

  self.num_keys = [

  key._1, key._2, key._3, key._4, key._5,

  key._6, key._7, key._8, key._9, key._0]

  # Instance of the model that handles the world.

  self.model = Model()

  # The label that is displayed in the top left of the canvas.

  self.label = pyglet.text.Label('', font_name='Arial', font_size=18,

  x=10, y=self.height - 10, anchor_x='left', anchor_y='top',

  color=(0, 0, 0, 255))

  # This call schedules the `update()` method to be called

  # TICKS_PER_SEC. This is the main game event loop.

  pyglet.clock.schedule_interval(self.update, 1.0 / TICKS_PER_SEC)

  def set_exclusive_mouse(self, exclusive):

  """ If `exclusive` is True, the game will capture the mouse, if False

  the game will ignore the mouse.

  """

  super(Window, self).set_exclusive_mouse(exclusive)

  self.exclusive = exclusive

  def get_sight_vector(self):

  """ Returns the current line of sight vector indicating the direction

  the player is looking.

  """

  x, y = self.rotation

  # y ranges from -90 to 90, or -pi/2 to pi/2, so m ranges from 0 to 1 and

  # is 1 when looking ahead parallel to the ground and 0 when looking

  # straight up or down.

  m = math.cos(math.radians(y))

  # dy ranges from -1 to 1 and is -1 when looking straight down and 1 when

  # looking straight up.

  dy = math.sin(math.radians(y))

  dx = math.cos(math.radians(x - 90)) * m

  dz = math.sin(math.radians(x - 90)) * m

  return (dx, dy, dz)

  def get_motion_vector(self):

  """ Returns the current motion vector indicating the velocity of the

  player.

  Returns

  -------

  vector : tuple of len 3

  Tuple containing the velocity in x, y, and z respectively.

  """

  if any(self.strafe):

  x, y = self.rotation

  strafe = math.degrees(math.atan2(*self.strafe))

  y_angle = math.radians(y)

  x_angle = math.radians(x + strafe)

  if self.flying:

  m = math.cos(y_angle)

  dy = math.sin(y_angle)

  if self.strafe[1]:

  # Moving left or right.

  dy = 0.0

  m = 1

  if self.strafe[0] > 0:

  # Moving backwards.

  dy *= -1

  # When you are flying up or down, you have less left and right

  # motion.

  dx = math.cos(x_angle) * m

  dz = math.sin(x_angle) * m

  else:

  dy = 0.0

  dx = math.cos(x_angle)

  dz = math.sin(x_angle)

  else:

  dy = 0.0

  dx = 0.0

  dz = 0.0

  return (dx, dy, dz)

  def update(self, dt):

  """ This method is scheduled to be called repeatedly by the pyglet

  clock.

  Parameters

  ----------

  dt : float

  The change in time since the last call.

  """

  self.model.process_queue()

  sector = sectorize(self.position)

  if sector != self.sector:

  self.model.change_sectors(self.sector, sector)

  if self.sector is None:

  self.model.process_entire_queue()

  self.sector = sector

  m = 8

  dt = min(dt, 0.2)

  for _ in xrange(m):

  self._update(dt / m)

  def _update(self, dt):

  """ Private implementation of the `update()` method. This is where most

  of the motion logic lives, along with gravity and collision detection.

  Parameters

  ----------

  dt : float

  The change in time since the last call.

  """

  # walking

  speed = FLYING_SPEED if self.flying else WALKING_SPEED

  d = dt * speed # distance covered this tick.

  dx, dy, dz = self.get_motion_vector()

  # New position in space, before accounting for gravity.

  dx, dy, dz = dx * d, dy * d, dz * d

  # gravity

  if not self.flying:

  # Update your vertical speed: if you are falling, speed up until you

  # hit terminal velocity; if you are jumping, slow down until you

  # start falling.

  self.dy -= dt * GRAVITY

  self.dy = max(self.dy, -TERMINAL_VELOCITY)

  dy += self.dy * dt

  # collisions

  x, y, z = self.position

  x, y, z = self.collide((x + dx, y + dy, z + dz), PLAYER_HEIGHT)

  self.position = (x, y, z)

  def collide(self, position, height):

  """ Checks to see if the player at the given `position` and `height`

  is colliding with any blocks in the world.

  Parameters

  ----------

  position : tuple of len 3

  The (x, y, z) position to check for collisions at.

  height : int or float

  The height of the player.

  Returns

  -------

  position : tuple of len 3

  The new position of the player taking into account collisions.

  """

  # How much overlap with a dimension of a surrounding block you need to

  # have to count as a collision. If 0, touching terrain at all counts as

  # a collision. If .49, you sink into the ground, as if walking through

  # tall grass. If >= .5, you'll fall through the ground.

  pad = 0.25

  p = list(position)

  np = normalize(position)

  for face in FACES: # check all surrounding blocks

  for i in xrange(3): # check each dimension independently

  if not face[i]:

  continue

  # How much overlap you have with this dimension.

  d = (p[i] - np[i]) * face[i]

  if d < pad:

  continue

  for dy in xrange(height): # check each height

  op = list(np)

  op[1] -= dy

  op[i] += face[i]

  if tuple(op) not in self.model.world:

  continue

  p[i] -= (d - pad) * face[i]

  if face == (0, -1, 0) or face == (0, 1, 0):

  # You are colliding with the ground or ceiling, so stop

  # falling / rising.

  self.dy = 0

  break

  return tuple(p)

  def on_mouse_press(self, x, y, button, modifiers):

  """ Called when a mouse button is pressed. See pyglet docs for button

  amd modifier mappings.

  Parameters

  ----------

  x, y : int

  The coordinates of the mouse click. Always center of the screen if

  the mouse is captured.

  button : int

  Number representing mouse button that was clicked. 1 = left button,

  4 = right button.

  modifiers : int

  Number representing any modifying keys that were pressed when the

  mouse button was clicked.

  """

  if self.exclusive:

  vector = self.get_sight_vector()

  block, previous = self.model.hit_test(self.position, vector)

  if (button == mouse.RIGHT) or

  ((button == mouse.LEFT) and (modifiers & key.MOD_CTRL)):

  # ON OSX, control + left click = right click.

  if previous:

  self.model.add_block(previous, self.block)

  elif button == pyglet.window.mouse.LEFT and block:

  texture = self.model.world[block]

  if texture != STONE:

  self.model.remove_block(block)

  else:

  self.set_exclusive_mouse(True)

  def on_mouse_motion(self, x, y, dx, dy):

  """ Called when the player moves the mouse.

  Parameters

  ----------

  x, y : int

  The coordinates of the mouse click. Always center of the screen if

  the mouse is captured.

  dx, dy : float

  The movement of the mouse.

  """

  if self.exclusive:

  m = 0.15

  x, y = self.rotation

  x, y = x + dx * m, y + dy * m

  y = max(-90, min(90, y))

  self.rotation = (x, y)

  def on_key_press(self, symbol, modifiers):

  """ Called when the player presses a key. See pyglet docs for key

  mappings.

  Parameters

  ----------

  symbol : int

  Number representing the key that was pressed.

  modifiers : int

  Number representing any modifying keys that were pressed.

  """

  if symbol == key.W:

  self.strafe[0] -= 1

  elif symbol == key.S:

  self.strafe[0] += 1

  elif symbol == key.A:

  self.strafe[1] -= 1

  elif symbol == key.D:

  self.strafe[1] += 1

  elif symbol == key.SPACE:

  if self.dy == 0:

  self.dy = JUMP_SPEED

  elif symbol == key.ESCAPE:

  self.set_exclusive_mouse(False)

  elif symbol == key.TAB:

  self.flying = not self.flying

  elif symbol in self.num_keys:

  index = (symbol - self.num_keys[0]) % len(self.inventory)

  self.block = self.inventory[index]

  def on_key_release(self, symbol, modifiers):

  """ Called when the player releases a key. See pyglet docs for key

  mappings.

  Parameters

  ----------

  symbol : int

  Number representing the key that was pressed.

  modifiers : int

  Number representing any modifying keys that were pressed.

  """

  if symbol == key.W:

  self.strafe[0] += 1

  elif symbol == key.S:

  self.strafe[0] -= 1

  elif symbol == key.A:

  self.strafe[1] += 1

  elif symbol == key.D:

  self.strafe[1] -= 1

  def on_resize(self, width, height):

  """ Called when the window is resized to a new `width` and `height`.

  """

  # label

  self.label.y = height - 10

  # reticle

  if self.reticle:

  self.reticle.delete()

  x, y = self.width // 2, self.height // 2

  n = 10

  self.reticle = pyglet.graphics.vertex_list(4,

  ('v2i', (x - n, y, x + n, y, x, y - n, x, y + n))

  )

  def set_2d(self):

  """ Configure OpenGL to draw in 2d.

  """

  width, height = self.get_size()

  glDisable(GL_DEPTH_TEST)

  viewport = self.get_viewport_size()

  glViewport(0, 0, max(1, viewport[0]), max(1, viewport[1]))

  glMatrixMode(GL_PROJECTION)

  glLoadIdentity()

  glOrtho(0, max(1, width), 0, max(1, height), -1, 1)

  glMatrixMode(GL_MODELVIEW)

  glLoadIdentity()

  def set_3d(self):

  """ Configure OpenGL to draw in 3d.

  """

  width, height = self.get_size()

  glEnable(GL_DEPTH_TEST)

  viewport = self.get_viewport_size()

  glViewport(0, 0, max(1, viewport[0]), max(1, viewport[1]))

  glMatrixMode(GL_PROJECTION)

  glLoadIdentity()

  gluPerspective(65.0, width / float(height), 0.1, 60.0)

  glMatrixMode(GL_MODELVIEW)

  glLoadIdentity()

  x, y = self.rotation

  glRotatef(x, 0, 1, 0)

  glRotatef(-y, math.cos(math.radians(x)), 0, math.sin(math.radians(x)))

  x, y, z = self.position

  glTranslatef(-x, -y, -z)

  def on_draw(self):

  """ Called by pyglet to draw the canvas.

  """

  self.clear()

  self.set_3d()

  glColor3d(1, 1, 1)

  self.model.batch.draw()

  self.draw_focused_block()

  self.set_2d()

  self.draw_label()

  self.draw_reticle()

  def draw_focused_block(self):

  """ Draw black edges around the block that is currently under the

  crosshairs.

  """

  vector = self.get_sight_vector()

  block = self.model.hit_test(self.position, vector)[0]

  if block:

  x, y, z = block

  vertex_data = cube_vertices(x, y, z, 0.51)

  glColor3d(0, 0, 0)

  glPolygonMode(GL_FRONT_AND_BACK, GL_LINE)

  pyglet.graphics.draw(24, GL_QUADS, ('v3f/static', vertex_data))

  glPolygonMode(GL_FRONT_AND_BACK, GL_FILL)

  def draw_label(self):

  """ Draw the label in the top left of the screen.

  """

  x, y, z = self.position

  self.label.text = '%02d (%.2f, %.2f, %.2f) %d / %d' % (

  pyglet.clock.get_fps(), x, y, z,

  len(self.model._shown), len(self.model.world))

  self.label.draw()

  def draw_reticle(self):

  """ Draw the crosshairs in the center of the screen.

  """

  glColor3d(0, 0, 0)

  self.reticle.draw(GL_LINES)

  def setup_fog():

  """ Configure the OpenGL fog properties.

  """

  # Enable fog. Fog "blends a fog color with each rasterized pixel fragment's

  # post-texturing color."

  glEnable(GL_FOG)

  # Set the fog color.

  glFogfv(GL_FOG_COLOR, (GLfloat * 4)(0.5, 0.69, 1.0, 1))

  # Say we have no preference between rendering speed and quality.

  glHint(GL_FOG_HINT, GL_DONT_CARE)

  # Specify the equation used to compute the blending factor.

  glFogi(GL_FOG_MODE, GL_LINEAR)

  # How close and far away fog starts and ends. The closer the start and end,

  # the denser the fog in the fog range.

  glFogf(GL_FOG_START, 20.0)

  glFogf(GL_FOG_END, 60.0)

  def setup():

  """ Basic OpenGL configuration.

  """

  # Set the color of "clear", i.e. the sky, in rgba.

  glClearColor(0.5, 0.69, 1.0, 1)

  # Enable culling (not rendering) of back-facing facets -- facets that aren't

  # visible to you.

  glEnable(GL_CULL_FACE)

  # Set the texture minification/magnification function to GL_NEAREST (nearest

  # in Manhattan distance) to the specified texture coordinates. GL_NEAREST

  # "is generally faster than GL_LINEAR, but it can produce textured 图片

  # with sharper edges because the transition between texture elements is not

  # as smooth."

  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)

  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)

  setup_fog()

  def main():

  window = Window(width=1800, height=1600, caption='Pyglet', resizable=True)

  # Hide the mouse cursor and prevent the mouse from leaving the window.

  window.set_exclusive_mouse(True)

  setup()

  pyglet.app.run()

  if __name__ == '__main__':

  main()