Re: [Pyode-user] dependence upon position?

[Hart's A. <bha...@ya...>]

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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