Mercurial > skaapsteker
annotate skaapsteker/physics.py @ 103:aaef228b6358
Run kitsune, run! And by the running of the kitsune gravity is restored to normal.
| author | Simon Cross <hodgestar@gmail.com> |
|---|---|
| date | Mon, 04 Apr 2011 20:46:44 +0200 |
| parents | 449a9579ec7a |
| children | 12ce1d131a72 |
| rev | line source |
|---|---|
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1 """Model of gravity, acceleration, velocities and collisions. |
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2 |
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3 Works very closely with sprites/base.py. |
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4 """ |
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5 |
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6 import pygame.sprite |
| 53 | 7 import pygame.draw |
| 39 | 8 import pygame |
| 9 import time | |
| 66 | 10 from constants import DEBUG, EPSILON |
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11 |
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12 class Sprite(pygame.sprite.DirtySprite): |
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13 |
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14 # physics attributes |
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15 mobile = True # whether the velocity may be non-zero |
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16 gravitates = True # whether gravity applies to the sprite |
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17 terminal_velocity = (300.0, 300.0) # maximum horizontal and vertial speeds (pixels / s) |
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18 bounce_factor = (0.98, 1.05) # bounce factor |
| 39 | 19 |
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20 # collision attributes |
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21 # Sprite X collides with Y iff (X.collision_layer in Y.collides_with) and X.check_collides(Y) |
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22 # Collisions result in the colliding movement being partially backed out, a call to X.bounce(frac) and a call to X.collided(Y) |
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23 # X.bounce(frac) is only called for the first (as determined by backing out distance) collision in a multi-collision event |
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24 collision_layer = None # never collides with anything |
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25 collides_with = set() # nothing collides with this |
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26 |
| 39 | 27 def __init__(self, *args, **kwargs): |
| 28 super(Sprite, self).__init__(*args, **kwargs) | |
| 29 self.velocity = (0.0, 0.0) | |
| 30 self.rect = pygame.Rect(0, 0, 10, 10) # sub-classes should override | |
| 43 | 31 self.image = pygame.Surface((10, 10)) |
| 32 self.image.fill((0, 0, 200)) | |
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33 self.visible = 1 |
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34 self.dirty = 1 |
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35 self.blendmode = 0 |
| 66 | 36 |
| 37 def init_pos(self): | |
| 38 self._float_pos = self.rect.topleft | |
| 39 | 39 |
| 53 | 40 def draw_debug(self, surface): |
| 41 pygame.draw.rect(surface, (240, 0, 0), self.rect, 1) | |
| 42 | |
| 39 | 43 def deltav(self, dv): |
| 44 v_x, v_y = self.velocity | |
| 45 v_x, v_y = v_x + dv[0], v_y + dv[1] | |
| 46 | |
| 47 t_v = self.terminal_velocity | |
| 48 v_x = max(min(v_x, t_v[0]), -t_v[0]) | |
| 49 v_y = max(min(v_y, t_v[1]), -t_v[1]) | |
| 50 | |
| 51 self.velocity = (v_x, v_y) | |
| 52 | |
| 53 def deltap(self, dt): | |
| 54 v_x, v_y = self.velocity | |
| 66 | 55 f_x, f_y = self._float_pos |
| 39 | 56 d_x, d_y = v_x * dt, v_y * dt |
| 66 | 57 f_x, f_y = f_x + d_x, f_y + d_y |
| 58 self._float_pos = f_x, f_y | |
| 59 self.rect.topleft = int(f_x), int(f_y) | |
| 60 | |
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61 def check_collides(self, other): |
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62 return True # default to relying purefly on collision_layer and collides_with |
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63 |
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64 def collided(self, other): |
| 98 | 65 pass |
| 66 | 66 |
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67 def bounce(self, other, normal): |
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68 """Alter velocity after a collision. |
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69 |
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70 other: sprite collided with |
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71 normal: unit vector (tuple) normal to the collision |
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72 surface. |
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73 """ |
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74 v_x, v_y = self.velocity |
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75 b_x = 1.0 + self.bounce_factor[0] * other.bounce_factor[0] |
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76 b_y = 1.0 + self.bounce_factor[1] * other.bounce_factor[1] |
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77 v_x = (1.0 - normal[0] * b_x) * v_x |
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78 v_y = (1.0 - normal[1] * b_y) * v_y |
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79 self.velocity = v_x, v_y |
| 39 | 80 |
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81 |
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82 class World(object): |
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83 |
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84 GRAVITY = 0.0, 9.8 * 20.0 # pixels / s^2 |
| 39 | 85 |
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86 def __init__(self): |
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87 self._all = pygame.sprite.LayeredUpdates() |
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88 self._mobiles = pygame.sprite.Group() |
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89 self._gravitators = pygame.sprite.Group() |
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90 self._collision_groups = { None: pygame.sprite.Group() } |
| 39 | 91 self._last_time = None |
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92 |
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93 def add(self, sprite): |
| 66 | 94 sprite.init_pos() |
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95 self._all.add(sprite) |
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96 if sprite.mobile: |
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97 self._mobiles.add(sprite) |
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98 if sprite.gravitates: |
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99 self._gravitators.add(sprite) |
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100 self._add_collision_group(sprite.collision_layer) |
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101 for layer in sprite.collides_with: |
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102 self._add_collision_group(layer) |
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103 self._collision_groups[layer].add(sprite) |
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104 |
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105 def _add_collision_group(self, layer): |
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106 if layer in self._collision_groups: |
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107 return |
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108 self._collision_groups[layer] = pygame.sprite.Group() |
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109 |
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110 def _backout_collisions(self, sprite, others, dt): |
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111 frac, normal, idx = 0.0, None, None |
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112 v_x, v_y = sprite.velocity |
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113 abs_v_x, abs_v_y = abs(v_x), abs(v_y) |
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114 |
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115 for i, other in enumerate(others): |
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116 clip = sprite.rect.clip(other.rect) |
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117 # TODO: avoid continual "if abs_v_? > EPSILON" |
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118 frac_x = clip.width / abs_v_x if abs_v_x > EPSILON else dt |
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119 frac_y = clip.height / abs_v_y if abs_v_y > EPSILON else dt |
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120 if frac_x > frac_y: |
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121 if frac_y > frac: |
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122 frac, normal, idx = frac_y, (0, 1), i |
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123 else: |
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124 if frac_x > frac: |
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125 frac, normal, idx = frac_x, (1, 0), i |
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126 |
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127 sprite.deltap(max(-1.1 * frac, -dt)) |
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128 sprite.bounce(others[idx], normal) |
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129 for other in others: |
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130 sprite.collided(other) |
| 39 | 131 |
| 132 def update(self): | |
| 133 if self._last_time is None: | |
| 134 self._last_time = time.time() | |
| 135 return | |
| 136 | |
| 137 # find dt | |
| 138 now = time.time() | |
| 139 self._last_time, dt = now, now - self._last_time | |
| 140 | |
| 141 # gravity | |
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142 dv = self.GRAVITY[0] * dt, self.GRAVITY[1] * dt |
| 39 | 143 for sprite in self._gravitators: |
| 144 sprite.deltav(dv) | |
| 145 | |
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146 # position update and collision check (do last) |
| 39 | 147 for sprite in self._mobiles: |
| 148 sprite.deltap(dt) | |
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149 sprite_collides = sprite.rect.colliderect |
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150 collisions = [] |
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151 for other in self._collision_groups[sprite.collision_layer]: |
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152 if sprite_collides(other) and sprite.check_collides(other): |
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153 collisions.append(other) |
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154 if collisions: |
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a1d95c6152a0
Shiny new collision detection. Read code for usage information.
Simon Cross <hodgestar@gmail.com>
parents:
85
diff
changeset
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155 self._backout_collisions(sprite, collisions, dt) |
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50
7d411ed02eac
Initial stab at detecting collisions.
Simon Cross <hodgestar@gmail.com>
parents:
43
diff
changeset
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156 |
| 39 | 157 def draw(self, surface): |
| 158 self._all.draw(surface) | |
| 53 | 159 if DEBUG: |
| 160 for sprite in self._all: | |
| 161 sprite.draw_debug(surface) |