Re: [Visualpython-users] strange math

[Lenore H. <lh...@si...>]

Sorry.  I was in too big a hurry and forgot to paste the code.  Here  
it is.  I've put arrows off to the right indicating the lines where  
both air.acceleration and pixie.acceleration are being changed despite  
the fact that only air.acceleration appears in the code.  I've  
included all of the while loop.  I don't see anywhere that I'm  
reassigning pixie.acceleration from its original value of gravity but  
it changes as soon as it hits those to statements (and not before).

Thanks,
Lenore


angle = math.pi/4
speed = 13.0

power = 2
constant = 1

gravity = vector(0,-9.8,0)

launch_velocity = vector(speed*math.cos(angle),speed*math.sin(angle),0)

pixie = sphere(pos=vector(-9,-3.55,0), radius=0.2, color=color.red)
pixie.velocity = launch_velocity
pixie.acceleration = gravity

air = sphere(pos=vector(-9,-3.55,0.3), radius=0.15, color=color.blue)
air.velocity = launch_velocity
air.acceleration = gravity

scene.mouse.getclick()    # Don't launch until we're watching

dt = 0.01
while 1:
     rate(100)
     air.pos = air.pos + air.velocity*dt
     if air.y < -3.55:
         air.velocity = vector(0,0,0)
     else:
         air.velocity = air.velocity + air.acceleration*dt
         air.acceleration.y = gravity.y - sign(air.velocity.y) *  
constant * air.radius * air.velocity.y**power    <-----
         print  "5", air.acceleration, pixie.acceleration
         air.acceleration.x = -sign(air.velocity.x) * constant *  
air.radius * air.velocity.x**power              <-------
         print "6", air.acceleration, pixie.acceleration

     pixie.pos = pixie.pos + pixie.velocity*dt
     if pixie.y < -3.55:
         pixie.velocity = vector(0,0,0)
     else:
         pixie.velocity = pixie.velocity + pixie.acceleration*dt


On Sep 11, 2009, at 18:20 , Bruce Sherwood wrote:

> Can you explain the context of your question? I have no idea what  
> program or
> documentation you're referring to.
>
> Bruce Sherwood
>
> Lenore Horner wrote:
>> Perhaps I'm just blind, but I can't figure out why the assignment
>> statements above print "5" and print "6" affect both acceleration
>> vectors, but they do.  How do I change the acceleration vector of one
>> object without touching the vector of other objects?
>>
>> Thanks,
>> Lenore
>
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