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#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
An attempt at some simple, self-contained pygame-based examples.
Example 01
In short:
One static body: a big polygon to represent the ground
One dynamic body: a rotated big polygon
And some drawing code to get you going.
kne
"""
import pygame
from pygame.locals import (QUIT, KEYDOWN, K_ESCAPE)
import Box2D # The main library
# Box2D.b2 maps Box2D.b2Vec2 to vec2 (and so on)
from Box2D.b2 import (world, polygonShape, staticBody, dynamicBody)
# --- constants ---
# Box2D deals with meters, but we want to display pixels,
# so define a conversion factor:
PPM = 20.0 # pixels per meter
TARGET_FPS = 60
TIME_STEP = 1.0 / TARGET_FPS
SCREEN_WIDTH, SCREEN_HEIGHT = 640, 480
# --- pygame setup ---
screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT), 0, 32)
pygame.display.set_caption('Simple pygame example')
clock = pygame.time.Clock()
# --- pybox2d world setup ---
# Create the world
world = world(gravity=(0, -10), doSleep=True)
# And a static body to hold the ground shape
ground_body = world.CreateStaticBody(
position=(0, 1),
shapes=polygonShape(box=(50, 5)),
)
# Create a dynamic body
dynamic_body = world.CreateDynamicBody(position=(10, 15), angle=15)
# And add a box fixture onto it (with a nonzero density, so it will move)
box = dynamic_body.CreatePolygonFixture(box=(2, 1), density=1, friction=0.3)
colors = {
staticBody: (255, 255, 255, 255),
dynamicBody: (127, 127, 127, 255),
}
# --- main game loop ---
running = True
while running:
# Check the event queue
for event in pygame.event.get():
if event.type == QUIT or (event.type == KEYDOWN and event.key == K_ESCAPE):
# The user closed the window or pressed escape
running = False
screen.fill((0, 0, 0, 0))
# Draw the world
for body in (ground_body, dynamic_body): # or: world.bodies
# The body gives us the position and angle of its shapes
for fixture in body.fixtures:
# The fixture holds information like density and friction,
# and also the shape.
shape = fixture.shape
# Naively assume that this is a polygon shape. (not good normally!)
# We take the body's transform and multiply it with each
# vertex, and then convert from meters to pixels with the scale
# factor.
vertices = [(body.transform * v) * PPM for v in shape.vertices]
# But wait! It's upside-down! Pygame and Box2D orient their
# axes in different ways. Box2D is just like how you learned
# in high school, with positive x and y directions going
# right and up. Pygame, on the other hand, increases in the
# right and downward directions. This means we must flip
# the y components.
vertices = [(v[0], SCREEN_HEIGHT - v[1]) for v in vertices]
pygame.draw.polygon(screen, colors[body.type], vertices)
# Make Box2D simulate the physics of our world for one step.
# Instruct the world to perform a single step of simulation. It is
# generally best to keep the time step and iterations fixed.
# See the manual (Section "Simulating the World") for further discussion
# on these parameters and their implications.
world.Step(TIME_STEP, 10, 10)
# Flip the screen and try to keep at the target FPS
pygame.display.flip()
clock.tick(TARGET_FPS)
pygame.quit()
print('Done!')
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