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#!/usr/bin/env python
# http://pyode.sourceforge.net/tutorials/tutorial2.html
# pyODE example 2: Connecting bodies with joints
# modified by Gideon Klompje (removed literals and using
# 'ode.Mass.setSphereTotal' instead of 'ode.Mass.setSphere')
import ode
import pygame
from pygame.locals import QUIT, KEYDOWN
# Constants
WINDOW_RESOLUTION = (640, 480)
DRAW_SCALE = WINDOW_RESOLUTION[0] / 5
"""Factor to multiply physical coordinates by to obtain screen size in pixels"""
DRAW_OFFSET = (WINDOW_RESOLUTION[0] / 2, 50)
"""Screen coordinates (in pixels) that map to the physical origin (0, 0, 0)"""
BACKGROUND_COLOR = (255, 255, 255)
GRAVITY = (0, -9.81, 0)
SPHERE1_POSITION = (1, 0, 0)
SPHERE1_MASS = 1
SPHERE1_RADIUS = 0.15
SPHERE1_COLOR = (55, 0, 200)
SPHERE2_POSITION = (2, 0, 0)
SPHERE2_MASS = 1
SPHERE2_RADIUS = 0.15
SPHERE2_COLOR = (55, 0, 200)
JOINT1_ANCHOR = (0, 0, 0)
JOINT1_COLOR = (200, 0, 55)
JOINT1_WIDTH = 2
"""Width of the line (in pixels) representing the joint"""
JOINT2_ANCHOR = SPHERE1_POSITION
JOINT2_COLOR = (200, 0, 55)
JOINT2_WIDTH = 2
"""Width of the line (in pixels) representing the joint"""
TIME_STEP = 0.04
# Utility functions
def coord(x, y, integer=False):
"""
Convert world coordinates to pixel coordinates. Setting 'integer' to
True will return integer coordinates.
"""
xs = (DRAW_OFFSET[0] + DRAW_SCALE*x)
ys = (DRAW_OFFSET[1] - DRAW_SCALE*y)
if integer:
return int(round(xs)), int(round(ys))
else:
return xs, ys
# Initialize pygame
pygame.init()
# Open a display
screen = pygame.display.set_mode(WINDOW_RESOLUTION)
# Create a world object
world = ode.World()
world.setGravity(GRAVITY)
# Create two bodies
body1 = ode.Body(world)
M = ode.Mass()
M.setSphereTotal(SPHERE1_MASS, SPHERE1_RADIUS)
body1.setMass(M)
body1.setPosition(SPHERE1_POSITION)
body2 = ode.Body(world)
M = ode.Mass()
M.setSphereTotal(SPHERE2_MASS, SPHERE2_RADIUS)
body2.setMass(M)
body2.setPosition(SPHERE2_POSITION)
# Connect body1 with the static environment
j1 = ode.BallJoint(world)
j1.attach(body1, ode.environment)
j1.setAnchor(JOINT1_ANCHOR)
# Connect body2 with body1
j2 = ode.BallJoint(world)
j2.attach(body1, body2)
j2.setAnchor(JOINT2_ANCHOR)
# Simulation loop...
if __name__ == "__main__":
fps = 1.0 / TIME_STEP
clk = pygame.time.Clock()
sph1_rad = int(DRAW_SCALE * SPHERE1_RADIUS)
sph2_rad = int(DRAW_SCALE * SPHERE2_RADIUS)
loopFlag = True
while loopFlag:
for e in pygame.event.get():
if e.type==QUIT:
loopFlag=False
if e.type==KEYDOWN:
loopFlag=False
# Clear the screen
screen.fill(BACKGROUND_COLOR)
# Draw the two bodies and the lines representing the joints
x1, y1, z1 = body1.getPosition()
x2, y2, z2 = body2.getPosition()
xj1, yj1, zj1 = j1.getAnchor()
xj2, yj2, zj2 = j2.getAnchor()
pygame.draw.line(screen, JOINT1_COLOR, coord(xj1, yj1), coord(x1, y1), JOINT1_WIDTH)
pygame.draw.line(screen, JOINT2_COLOR, coord(xj2, yj2), coord(x2, y2), JOINT2_WIDTH)
pygame.draw.circle(screen, SPHERE1_COLOR, coord(x1, y1, integer=True), sph1_rad, 0)
pygame.draw.circle(screen, SPHERE2_COLOR, coord(x2, y2, integer=True), sph2_rad, 0)
pygame.display.flip()
# Next simulation step
world.step(TIME_STEP)
# Try to keep the specified framerate
clk.tick(fps)
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