RE: [Pyode-user] General question about ode

[Paul K. <pki...@in...>]

From memory - you need to keep a global copy of your joint (since pyode
doesn't store them).  Your joints are potentially being destroyed when
drop_object() exists.
 
Paul
 
-----Original Message-----
From: pyo...@li...
[mailto:pyo...@li...] On Behalf Of Ricardo
Kirkner
Sent: Friday, 28 October 2005 8:08 AM
To: pyo...@li...
Subject: [Pyode-user] General question about ode
 
Hi:

I am really new to this ode/pyode thing. I am trying to develop a
simulation using pyode. I finally made it (using several "borrowed
example code" :-)) to have my objects get rendered on screen.

They are currently generated a bit above the ground, so when I rendered
them, they fall a little (inspired by the pyode tutorial2). I have
created a model that consists of two boxes that should be connected
through a stick. All three objects get correctly rendered, but they
don't keep together (they just split apart as soon as they fall on the
ground)

The code I am using to created those objects is:

------------------------------------------------------------------------
-----------------------------------------------
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

def drop_object():
    """Drop an object into the scene."""
    
    global bodies
    
    blockA = create_box(world, space, 1000, 1.0,1.0,1.0)
    blockB = create_box(world, space, 1000, 1.0,1.0,1.0)
    link = create_box(world, space, 1000, 1.0, 0.2, 0.2)
    x, y, z = 0.0, 1.0, 0.0
    blockA.setPosition( (x,y,z ))
    link.setPosition((x+1,y,z))
    blockB.setPosition((x+2,y,z))
    m = mat4().rotation(0, (0,1,0))
    blockA.setRotation(m.toList())
    blockB.setRotation(m.toList())
    link.setRotation(m.toList())

    j1 = ode.HingeJoint(world)
    j2 = ode.HingeJoint(world)
    j1.attach(blockA, link)
    j2.attach(blockB, link)
    j1.setAnchor((0,0,0))
    j2.setAnchor((1,0,0))
    j1.setAxis((0,0,1))
    j2.setAxis((0,0,1))
    j1.setParam(ode.ParamFMax, ode.Infinity)
    j1.setParam(ode.ParamVel, 0)
    j2.setParam(ode.ParamFMax, ode.Infinity)
    j2.setParam(ode.ParamVel, 0)
        
    bodies.append(blockA)
    bodies.append(blockB)
    bodies.append(link)

------------------------------------------------------------------------
-----------------------------------------------

Maybe someone can help me to get this three objects remain connected all
time? Maybe I should have written to the ode mailing list, but since I
am writing code in python, I thought of this one.

With regards,

Ricardo Kirkner