Re: [Pyode-user] dependence upon position?

[<mi...@mi...>]

Thank you. I'll look into that.

- Miriam

> setting your worlds ERP and CFM to zero seems to fix this, not sure why tho..
> -brett
>
>
> --- mi...@mi... wrote:
>
> > Hi folks,
> >
> > A friend (he's probably joining pyode-user as I send this) sent me the two small python scripts
> > (attached). They both drop a block near another. They are the same except for one being at
> > (0,0,0) the other at (10,10,10), but their behavior is markedly different. Why?
> >
> > Is there any way to ensure that behavior has positional independence? ...at least in fairly
> > ordinary ranges. I know things will get crazy near the limits of numerical precision, but this
> > is just a little over 10 units from the center of the universe.
> >
> > Is there some other parameter that needs to be handled to take account of the position?
> >
> > Best wishes,
> >
> >     - Miriam
> > --
> > ---------=---------=---------=---------=---------=---------=------
> > A life! Cool! Where can I download one of those from?
> > ---------=---------=---------=---------=---------=---------=------
> > Website: http://miriam-english.org
> > Blog: http://www.livejournal.com/users/miriam_e/
> > > # pyODE example 3: Collision detection
> > # origin
> >
> > # Originally by Matthias Baas.
> > # Updated by Pierre Gay to work without pygame or cgkit.
> >
> > import sys, os, random, time
> > from math import *
> > from OpenGL.GL import *
> > from OpenGL.GLU import *
> > from OpenGL.GLUT import *
> >
> > import ode
> >
> > # geometric utility functions
> > def scalp (vec, scal):
> >     vec[0] *= scal
> >     vec[1] *= scal
> >     vec[2] *= scal
> >
> > def length (vec):
> >     return sqrt (vec[0]**2 + vec[1]**2 + vec[2]**2)
> >
> > # prepare_GL
> > def prepare_GL():
> >     """Prepare drawing.
> >     """
> >
> >     # Viewport
> >     glViewport(0,0,640,480)
> >
> >     # Initialize
> >     glClearColor(0.8,0.8,0.9,0)
> >     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
> >     glEnable(GL_DEPTH_TEST)
> >     glDisable(GL_LIGHTING)
> >     glEnable(GL_LIGHTING)
> >     glEnable(GL_NORMALIZE)
> >     glShadeModel(GL_FLAT)
> >
> >     # Projection
> >     glMatrixMode(GL_PROJECTION)
> >     glLoadIdentity()
> >     gluPerspective (45,1.3333,0.2,20)
> >
> >     # Initialize ModelView matrix
> >     glMatrixMode(GL_MODELVIEW)
> >     glLoadIdentity()
> >
> >     # Light source
> >     glLightfv(GL_LIGHT0,GL_POSITION,[0,0,1,0])
> >     glLightfv(GL_LIGHT0,GL_DIFFUSE,[1,1,1,1])
> >     glLightfv(GL_LIGHT0,GL_SPECULAR,[1,1,1,1])
> >     glEnable(GL_LIGHT0)
> >
> >     # View transformation
> >     gluLookAt (2.4, 3.6, 4.8, 0.5, 0.5, 0, 0, 1, 0)
> >
> > # draw_body
> > def draw_body(body):
> >     """Draw an ODE body.
> >     """
> >
> >     x,y,z = body.getPosition()
> >     R = body.getRotation()
> >     #rot = [R[0], R[3], R[6], 0.,
> >     #       R[1], R[4], R[7], 0.,
> >     #       R[2], R[5], R[8], 0.,
> >     #       x, y, z, 1.0]
> >     rot = [1, 0.0, 0.0, 0.0,
> >            0.0, 1, 0.0, 0.0,
> >            0.0, 0.0, 1.0, 0.0,
> >            x, y, z, 1.0]
> >     glPushMatrix()
> >     glMultMatrixd(rot)
> >     if body.shape=="box":
> >         sx,sy,sz = body.boxsize
> >         glScale(sx, sy, sz)
> >         glutSolidCube(1)
> >     glPopMatrix()
> >
> >
> > # create_box
> > def create_box(world, space, density, lx, ly, lz):
> >     """Create a box body and its corresponding geom."""
> >
> >     # Create body
> >     body = ode.Body(world)
> >     M = ode.Mass()
> >     M.setBox(density, lx, ly, lz)
> >     body.setMass(M)
> >
> >     # Set parameters for drawing the body
> >     body.shape = "box"
> >     body.boxsize = (lx, ly, lz)
> >
> >     # Create a box geom for collision detection
> >     geom = ode.GeomBox(space, lengths=body.boxsize)
> >     geom.setBody(body)
> >
> >     return body
> >
> > # create box object
> > def create_object(posx, posy, posz):
> >     """create one box at a given position."""
> >
> >     global bodies, counter, objcount
> >
> >     body = create_box(world, space, 1000, 1.0,1.0,1.0)
> >     body.setPosition((posx, posy, posz))
> >     bodies.append(body)
> >     #counter=0
> >     objcount+=1
> >
> >
> > # drop_object
> > def drop_object(posx, posy, posz):
> >     """Drop an object into the scene."""
> >
> >     global bodies, counter, objcount
> >
> >     body = create_box(world, space, 1000, 1.0,1.0,1.0)
> >     body.setPosition((posx, posy, posz))
> >     bodies.append(body)
> >     #counter=0
> >     objcount+=1
> >
> > # Collision callback
> > def near_callback(args, geom1, geom2):
> >     """Callback function for the collide() method.
> >
> >     This function checks if the given geoms do collide and
> >     creates contact joints if they do.
> >     """
> >
> >     # Check if the objects do collide
> >     contacts = ode.collide(geom1, geom2)
> >
> >     # Create contact joints
> >     world,contactgroup = args
> >     for c in contacts:
> >         c.setBounce(0.2)
> >         c.setMu(5000)
> >         j = ode.ContactJoint(world, contactgroup, c)
> >         j.attach(geom1.getBody(), geom2.getBody())
> >
> >
> >
> > ######################################################################
> >
> > # Initialize Glut
> > glutInit ([])
> >
> > # Open a window
> > glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE)
> >
> > x = 0
> > y = 0
> > width = 640
> > height = 480
> > glutInitWindowPosition (x, y);
> > glutInitWindowSize (width, height);
> > glutCreateWindow ("(0,0,0)")
> >
> > # Create a world object
> > world = ode.World()
> > world.setGravity( (0,-9.81,0) )
> > world.setERP(0.8)
> > world.setCFM(1E-5)
> >
> > # Create a space object
> > space = ode.Space()
> >
> > # Create a plane geom which prevent the objects from falling forever
> > floor = ode.GeomPlane(space, (0,1,0), 0)
> >
> > # A list with ODE bodies
> > bodies = []
> >
> > # A joint group for the contact joints that are generated whenever
> > # two bodies collide
> > contactgroup = ode.JointGroup()
> >
> > # Some variables used inside the simulation loop
> > fps = 50
> > dt = 1.0/fps
> > running = True
> > state = 0
> > counter = 0
> > objcount = 0
> > lasttime = time.time()
> >
> >
> > # keyboard callback
> > def _keyfunc (c, x, y):
> >     sys.exit (0)
> >
> > glutKeyboardFunc (_keyfunc)
> >
> > # draw callback
> > def _drawfunc ():
> >
> === message truncated ===> # pyODE example 3: Collision detection
> > # 1000
> >
> > # Originally by Matthias Baas.
> > # Updated by Pierre Gay to work without pygame or cgkit.
> >
> > import sys, os, random, time
> > from math import *
> > from OpenGL.GL import *
> > from OpenGL.GLU import *
> > from OpenGL.GLUT import *
> >
> > import ode
> >
> > # geometric utility functions
> > def scalp (vec, scal):
> >     vec[0] *= scal
> >     vec[1] *= scal
> >     vec[2] *= scal
> >
> > def length (vec):
> >     return sqrt (vec[0]**2 + vec[1]**2 + vec[2]**2)
> >
> > # prepare_GL
> > def prepare_GL():
> >     """Prepare drawing.
> >     """
> >
> >     # Viewport
> >     glViewport(0,0,640,480)
> >
> >     # Initialize
> >     glClearColor(0.8,0.8,0.9,0)
> >     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
> >     glEnable(GL_DEPTH_TEST)
> >     glDisable(GL_LIGHTING)
> >     glEnable(GL_LIGHTING)
> >     glEnable(GL_NORMALIZE)
> >     glShadeModel(GL_FLAT)
> >
> >     # Projection
> >     glMatrixMode(GL_PROJECTION)
> >     glLoadIdentity()
> >     gluPerspective (45,1.3333,0.2,20)
> >
> >     # Initialize ModelView matrix
> >     glMatrixMode(GL_MODELVIEW)
> >     glLoadIdentity()
> >
> >     # Light source
> >     glLightfv(GL_LIGHT0,GL_POSITION,[0,0,1,0])
> >     glLightfv(GL_LIGHT0,GL_DIFFUSE,[1,1,1,1])
> >     glLightfv(GL_LIGHT0,GL_SPECULAR,[1,1,1,1])
> >     glEnable(GL_LIGHT0)
> >
> >     # View transformation
> >     gluLookAt (12.4, 13.6, 14.8, 10.5, 10.5, 10, 0, 1, 0)
> >
> > # draw_body
> > def draw_body(body):
> >     """Draw an ODE body.
> >     """
> >
> >     x,y,z = body.getPosition()
> >     R = body.getRotation()
> >     #rot = [R[0], R[3], R[6], 0.,
> >     #       R[1], R[4], R[7], 0.,
> >     #       R[2], R[5], R[8], 0.,
> >     #       x, y, z, 1.0]
> >     rot = [1, 0.0, 0.0, 0.0,
> >            0.0, 1, 0.0, 0.0,
> >            0.0, 0.0, 1.0, 0.0,
> >            x, y, z, 1.0]
> >     glPushMatrix()
> >     glMultMatrixd(rot)
> >     if body.shape=="box":
> >         sx,sy,sz = body.boxsize
> >         glScale(sx, sy, sz)
> >         glutSolidCube(1)
> >     glPopMatrix()
> >
> >
> > # create_box
> > def create_box(world, space, density, lx, ly, lz):
> >     """Create a box body and its corresponding geom."""
> >
> >     # Create body
> >     body = ode.Body(world)
> >     M = ode.Mass()
> >     M.setBox(density, lx, ly, lz)
> >     body.setMass(M)
> >
> >     # Set parameters for drawing the body
> >     body.shape = "box"
> >     body.boxsize = (lx, ly, lz)
> >
> >     # Create a box geom for collision detection
> >     geom = ode.GeomBox(space, lengths=body.boxsize)
> >     geom.setBody(body)
> >
> >     return body
> >
> > # create box object
> > def create_object(posx, posy, posz):
> >     """create one box at a given position."""
> >
> >     global bodies, counter, objcount
> >
> >     body = create_box(world, space, 1000, 1.0,1.0,1.0)
> >     body.setPosition((posx, posy, posz))
> >     bodies.append(body)
> >     #counter=0
> >     objcount+=1
> >
> >
> > # drop_object
> > def drop_object(posx, posy, posz):
> >     """Drop an object into the scene."""
> >
> >     global bodies, counter, objcount
> >
> >     body = create_box(world, space, 1000, 1.0,1.0,1.0)
> >     body.setPosition((posx, posy, posz))
> >     bodies.append(body)
> >     #counter=0
> >     objcount+=1
> >
> > # Collision callback
> > def near_callback(args, geom1, geom2):
> >     """Callback function for the collide() method.
> >
> >     This function checks if the given geoms do collide and
> >     creates contact joints if they do.
> >     """
> >
> >     # Check if the objects do collide
> >     contacts = ode.collide(geom1, geom2)
> >
> >     # Create contact joints
> >     world,contactgroup = args
> >     for c in contacts:
> >         c.setBounce(0.2)
> >         c.setMu(5000)
> >         j = ode.ContactJoint(world, contactgroup, c)
> >         j.attach(geom1.getBody(), geom2.getBody())
> >
> >
> >
> > ######################################################################
> >
> > # Initialize Glut
> > glutInit ([])
> >
> > # Open a window
> > glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE)
> >
> > x = 0
> > y = 0
> > width = 640
> > height = 480
> > glutInitWindowPosition (x, y);
> > glutInitWindowSize (width, height);
> > glutCreateWindow ("(10,10,10)")
> >
> > # Create a world object
> > world = ode.World()
> > world.setGravity( (0,-9.81,0) )
> > world.setERP(0.8)
> > world.setCFM(1E-5)
> >
> > # Create a space object
> > space = ode.Space()
> >
> > # Create a plane geom which prevent the objects from falling forever
> > floor = ode.GeomPlane(space, (0,1,0), 10)
> >
> > # A list with ODE bodies
> > bodies = []
> >
> > # A joint group for the contact joints that are generated whenever
> > # two bodies collide
> > contactgroup = ode.JointGroup()
> >
> > # Some variables used inside the simulation loop
> > fps = 50
> > dt = 1.0/fps
> > running = True
> > state = 0
> > counter = 0
> > objcount = 0
> > lasttime = time.time()
> >
> >
> > # keyboard callback
> > def _keyfunc (c, x, y):
> >     sys.exit (0)
> >
> > glutKeyboardFunc (_keyfunc)
> >
> > # draw callback
> > def _drawfunc ():
> >
> === message truncated ===>
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