课程全名：An Introduction to Interactive Programming in Python，来自 Rice University
授课教授：Joe Warren, Scott Rixner, John Greiner, Stephen Wong
工具：http://www.codeskulptor.org/， simplegui 模块
最后两周就要结束了~~~
第七周：
先上图，这周完成Spaceship游戏的一部分。
在这图里面有什么？飞船，陨石，子弹，背景图….
用OO的对象来看，他们都对应一幅图像，那么抽象一个类ImageInfo来操作这些图像信息，它包括图像的center(中心位置)，size(图像大小)，radius(半径)，lifespan(时间周期)，animated(动画)。可能有些属性比较陌生，有些针对到具体的对象才有用。
class ImageInfo: def __init__(self, center, size, radius = 0, lifespan = None, animated = False): self.center = center self.size = size self.radius = radius if lifespan: self.lifespan = lifespan else: self.lifespan = float('inf') self.animated = animated def get_center(self): return self.center def get_size(self): return self.size def get_radius(self): return self.radius def get_lifespan(self): return self.lifespan def get_animated(self): return self.animated
有了图像的表示，那么我们还需要飞船，用Ship来表示
Ship有什么属性和方法呢？
pos：位置
vel：加速度
thrust：冲刺状态
angle：飞船旋转的角度
angle_vel：飞船旋转角速度
image：飞船图像
image_cener：飞船图像的中心位置
image_size：飞船图像的大小
image_radius：飞船半径？(这周作业没用到，不知道干嘛的)
飞船的方法：
draw(canvas): 绘制飞船，要求绘制根据是否在冲刺状态，绘制图像不同。所给的飞船image是tiled图像，所以绘制时候计算一下偏移就好
update()：更新当前飞船位置以及角度。基本所有涉及到简单数学计算的公式，课上以及相关ppt都给出来，都比较简单，直接拿来用。对于角度的更新和Pong那周一样，用左右按键按下增加旋转角速度，放开减少旋转角速度，每次更新的时候就只用把飞船的角度加上旋转角速度。
飞船的位置更新同理，使用位置加上加速度，但是要考虑飞出边界，所以对WIDTH和HEIGHT分别取模。
这边与Pong不同的是加速度的计算，Pong只有上下方向，但这里飞船可以旋转指向各个方向，所以加速度修改飞船向着它转角的方向，原理还是一样，把转角方向向水平和垂直方向做投影乘以常量，然后加到原有的加速度上。
最后剩下的一个问题就是，外太空有<阻力>，所以飞船会不断减速直到速度为0，那么不断按照一定的比例缩小飞船的加速度，直到加速度为0，飞船的位置就不更新了。
update()的代码如下:
def update(self): self.angle += self.angle_vel self.pos[0] = (self.pos[0] + self.vel[0]) % WIDTH self.pos[1] = (self.pos[1] + self.vel[1]) % HEIGHT c = 0.05 self.vel[0] *= (1 - c) self.vel[1] *= (1 - c) forward = angle_to_vector(self.angle) if self.thrust: self.vel[0] += forward[0] * 1.2 self.vel[1] += forward[1] * 1.2
change_angle_vel(ori, key_state)：根据按键是left或者right和按键当前状态是按下或者松开，来改变飞船的旋转角速度
set_thruster(thruster_state)：根据up按键来改变飞船的冲刺状态，并且播放和暂停响应的声音效果
shoot(): 飞船发子弹，初始化子弹，它的位置在飞船的炮孔位置，然后子弹的加速度等于，飞船的加速度，加上飞船角度在水平垂直分量的常量倍，这与飞船的加速思路一样的，子弹的角度和旋转角速度设置成0就好。
飞船处理完了，剩下的就是陨石和子弹，给的template中用sprite来抽象表示他们。
基本的属性和飞船差不多，pos, vel, angle, angle_vel, image, image_center, image_size, radius，多了lifespan, animated, age还有sound
主要方法：
draw(canvas): 直接根据image的信息进行绘制
update(canvas): 更新角度和位置，与飞船类似。超出边界要取模
其他的部分就是frame的draw事件模板里已经写好，key_up，key_down事件，上面也都提到处理方法。
这周的任务也就这样完工了。
完整的代码如下：
# program template for Spaceship import simplegui import math import random # globals for user interface WIDTH = 800 HEIGHT = 600 score = 0 lives = 3 time = 0.5 class ImageInfo: def __init__(self, center, size, radius = 0, lifespan = None, animated = False): self.center = center self.size = size self.radius = radius if lifespan: self.lifespan = lifespan else: self.lifespan = float('inf') self.animated = animated def get_center(self): return self.center def get_size(self): return self.size def get_radius(self): return self.radius def get_lifespan(self): return self.lifespan def get_animated(self): return self.animated # art assets created by Kim Lathrop, may be freely re-used in non-commercial projects, please credit Kim # debris images - debris1_brown.png, debris2_brown.png, debris3_brown.png, debris4_brown.png # debris1_blue.png, debris2_blue.png, debris3_blue.png, debris4_blue.png, debris_blend.png debris_info = ImageInfo([320, 240], [640, 480]) debris_image = simplegui.load_image("http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/debris2_blue.png") # nebula images - nebula_brown.png, nebula_blue.png nebula_info = ImageInfo([400, 300], [800, 600]) nebula_image = simplegui.load_image("http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/nebula_blue.f2014.png") # splash image splash_info = ImageInfo([200, 150], [400, 300]) splash_image = simplegui.load_image("http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/splash.png") # ship image ship_info = ImageInfo([45, 45], [90, 90], 35) ship_image = simplegui.load_image("http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/double_ship.png") # missile image - shot1.png, shot2.png, shot3.png missile_info = ImageInfo([5,5], [10, 10], 3, 50) missile_image = simplegui.load_image("http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/shot2.png") # asteroid images - asteroid_blue.png, asteroid_brown.png, asteroid_blend.png asteroid_info = ImageInfo([45, 45], [90, 90], 40) asteroid_image = simplegui.load_image("http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/asteroid_blue.png") # animated explosion - explosion_orange.png, explosion_blue.png, explosion_blue2.png, explosion_alpha.png explosion_info = ImageInfo([64, 64], [128, 128], 17, 24, True) explosion_image = simplegui.load_image("http://commondatastorage.googleapis.com/codeskulptor-assets/lathrop/explosion_alpha.png") # sound assets purchased from sounddogs.com, please do not redistribute soundtrack = simplegui.load_sound("http://commondatastorage.googleapis.com/codeskulptor-assets/sounddogs/soundtrack.mp3") missile_sound = simplegui.load_sound("http://commondatastorage.googleapis.com/codeskulptor-assets/sounddogs/missile.mp3") missile_sound.set_volume(.5) ship_thrust_sound = simplegui.load_sound("http://commondatastorage.googleapis.com/codeskulptor-assets/sounddogs/thrust.mp3") explosion_sound = simplegui.load_sound("http://commondatastorage.googleapis.com/codeskulptor-assets/sounddogs/explosion.mp3") # helper functions to handle transformations def angle_to_vector(ang): return [math.cos(ang), math.sin(ang)] def dist(p,q): return math.sqrt((p[0] - q[0]) ** 2+(p[1] - q[1]) ** 2) # Ship class class Ship: def __init__(self, pos, vel, angle, image, info): self.pos = [pos[0],pos[1]] self.vel = [vel[0],vel[1]] self.thrust = False self.angle = angle self.angle_vel = 0 self.image = image self.image_center = info.get_center() self.image_size = info.get_size() self.radius = info.get_radius() def draw(self,canvas): if self.thrust: center = (self.image_center[0]+self.image_size[0], self.image_center[1]) canvas.draw_image(self.image, center, self.image_size, self.pos, self.image_size, self.angle) else: canvas.draw_image(self.image, self.image_center, self.image_size, self.pos, self.image_size, self.angle) def update(self): self.angle += self.angle_vel self.pos[0] = (self.pos[0] + self.vel[0]) % WIDTH self.pos[1] = (self.pos[1] + self.vel[1]) % HEIGHT c = 0.05 self.vel[0] *= (1 - c) self.vel[1] *= (1 - c) forward = angle_to_vector(self.angle) if self.thrust: self.vel[0] += forward[0] * 1.2 self.vel[1] += forward[1] * 1.2 def change_angle_vel(self, ori, key_state): if ((ori == "right" and key_state == "keyup") or (ori == "left" and key_state == "keydown")): self.angle_vel -= 0.1 elif ((ori == "right" and key_state == "keydown") or (ori == "left" and key_state == "keyup")): self.angle_vel += 0.1 def set_thruster(self, thruster_state): self.thrust = thruster_state if self.thrust: ship_thrust_sound.rewind() ship_thrust_sound.play() else: ship_thrust_sound.rewind() def shoot(self): global a_missile offset = self.image_size[0] / 2.0 forward = angle_to_vector(self.angle) pos = [self.pos[0] + offset * forward[0], self.pos[1] + offset * forward[1]] vel = [self.vel[0] + 4 * forward[0], self.vel[1] + 4 * forward[1]] ang = 0 ang_vel = 0 a_missile = Sprite(pos, vel, ang, ang_vel, missile_image, missile_info, missile_sound) # Sprite class class Sprite: def __init__(self, pos, vel, ang, ang_vel, image, info, sound = None): self.pos = [pos[0],pos[1]] self.vel = [vel[0],vel[1]] self.angle = ang self.angle_vel = ang_vel self.image = image self.image_center = info.get_center() self.image_size = info.get_size() self.radius = info.get_radius() self.lifespan = info.get_lifespan() self.animated = info.get_animated() self.age = 0 if sound: sound.rewind() sound.play() def draw(self, canvas): canvas.draw_image(self.image, self.image_center, self.image_size, self.pos, self.image_size, self.angle) def update(self): self.angle += self.angle_vel self.pos[0] = (self.pos[0] + self.vel[0]) % WIDTH self.pos[1] = (self.pos[1] + self.vel[1]) % HEIGHT def draw(canvas): global time # animiate background time += 1 wtime = (time / 4) % WIDTH center = debris_info.get_center() size = debris_info.get_size() canvas.draw_image(nebula_image, nebula_info.get_center(), nebula_info.get_size(), [WIDTH / 2, HEIGHT / 2], [WIDTH, HEIGHT]) canvas.draw_image(debris_image, center, size, (wtime - WIDTH / 2, HEIGHT / 2), (WIDTH, HEIGHT)) canvas.draw_image(debris_image, center, size, (wtime + WIDTH / 2, HEIGHT / 2), (WIDTH, HEIGHT)) # draw ship and sprites my_ship.draw(canvas) a_rock.draw(canvas) a_missile.draw(canvas) # update ship and sprites my_ship.update() a_rock.update() a_missile.update() # draw lives canvas.draw_text("Lives", [WIDTH / 12, HEIGHT / 12], 30, "White") canvas.draw_text(str(lives), [WIDTH / 12, HEIGHT / 12 + 40], 30, "White") # draw score canvas.draw_text("Score", [10 * WIDTH / 12, HEIGHT/12], 30, "White") canvas.draw_text(str(score), [10 * WIDTH /12, HEIGHT/12 + 40], 30, "White") # timer handler that spawns a rock def rock_spawner(): global a_rock pos = [random.randint(0, WIDTH-1), random.randint(0, HEIGHT-1)] vel = [random.randrange(1, 5, 1)*random.choice([1, -1]), random.randrange(1, 5, 1)*random.choice([1, -1])] ang = 0 ang_vel = random.randrange(5, 10, 1) / 100.0 * random.choice([1, -1]) a_rock = Sprite(pos, vel, ang, ang_vel, asteroid_image, asteroid_info) def key_up(key): if simplegui.KEY_MAP['left'] == key: my_ship.change_angle_vel("left", "keyup") elif simplegui.KEY_MAP['right'] == key: my_ship.change_angle_vel("right", "keyup") elif simplegui.KEY_MAP['up'] == key: my_ship.set_thruster(False) def key_down(key): if simplegui.KEY_MAP['left'] == key: my_ship.change_angle_vel("left", "keydown") elif simplegui.KEY_MAP['right'] == key: my_ship.change_angle_vel("right", "keydown") elif simplegui.KEY_MAP['up'] == key: my_ship.set_thruster(True) elif simplegui.KEY_MAP['space'] == key: my_ship.shoot() # initialize frame frame = simplegui.create_frame("Asteroids", WIDTH, HEIGHT) # initialize ship and two sprites my_ship = Ship([WIDTH / 2, HEIGHT / 2], [0, 0], 0, ship_image, ship_info) a_rock = Sprite([WIDTH / 3, HEIGHT / 3], [1, 1], 0, 0, asteroid_image, asteroid_info) a_missile = Sprite([2 * WIDTH / 3, 2 * HEIGHT / 3], [-1, 1], 0, 0, missile_image, missile_info, missile_sound) # register handlers frame.set_draw_handler(draw) frame.set_keydown_handler(key_down) frame.set_keyup_handler(key_up) timer = simplegui.create_timer(1000.0, rock_spawner) # get things rolling timer.start() frame.start()
期待着最后一周，游戏完整的代码。就要完成Coursera的一门这么有意思的课，课程难度很小，乐趣十足。