[Edu-sig] More code for VPython (beginner)

[kirby urner]

Below (appended code) is the kind of thing I use to introduce VPython,
some high school math hoped for, in that there's a little bit of trig,
an allusion to complex numbers.

The fun here is VPython lets us put colorful geometric objects on
screen then change their position at runtime, so it's not like some
ray tracing program.  So you can have a ball traveling around in a
ring, or clock hands and stuff, all without any overwhelming amount of
code.

Six working examples in under 200 lines, including blank ones, ain't
bad.  But then I don't try out all the objects.  This is a genre
nothing exhaustive -- one could imagine thousands of such examples in
a database somewhere.

Another example on YouTube:
http://www.youtube.com/watch?v=QXCPDsBN2Kc  (looks like an obelisk,
thinking of the late Arthur C.C.).

Dr. Sonnenfeld in New Mexico provides the source underneath but
Youtube de-indents for us, so here it is again:

from visual import *
from random import randint

thecolors = [color.green, color.red, color.orange, color.magenta]

for i in range(10000):
   place = (randint(-100,100), randint(-100, 100), randint(-10,10))
   rcolor = randint(0,3)
   ball = sphere(pos = place, radius=0.5, color = thecolors[rcolor])

You can just hit F5 in IDLE's text editor and it'll run.  Likewise for
the examples below, I have students go to the bottom and progressively
uncomment each test, hit F5 to run, always in the same IDLE session
(shell restarts by itself, upon close of VPython window, very smooth).

Dunno who many of you are using VPython in classes.  I've got a
Windows lab going at the local university with Python 2.5, VPython,
POV-Ray on every workstation.

For those on this list for a long time:  Arthur Siegel wrote the most
ambitious projective geometry package in Python, starting from his own
fascination with that subject (not programming per se, he came from
financial circles), and we used to argue about whether VPython should
just be a part of the standard library, given how powerful it is (we
argued about a lot of things -- miss the guy, he died very suddenly,
the website is here:  http://pygeo.sourceforge.net/ ).

I do find that easy access to an OpenGL type space does marvels for
language appeal, and given I'm recruiting in the open market, I'm glad
to have VPython in my toolkit, really helps make my Saturday Academy
class a viable elective.  All the buzz about Python in general also
helps of course.

Kirby
4D
Portland, Oregon

"""
Stuff to do with VPython
vpython.org

by Kirby Urner
4D Solutions
4dsolutions.net

May 2, 2008

If you're on the Internet, why not keep a
link to the documentation handy in your
browser.
"""

from visual import *  # get a lot of stuff

import math     # definitely wanna have math in the picture

def stage():
     scene = display(title='VPython Window',
     width=600, height=600,
     center=(0,0,0), background=(0,1,1))
     return scene


def firsttry():  # no arguments here
    """
    The cylinder Object

    """

    s = stage()
    s.autoscale = 0
    s.scale = (0.5, 0.5, 0.5)  # we figure out a good view
    s.select()

    rod = cylinder(pos=(0,0,0), axis=(5,0,0), radius=0.1)
    rod.color = color.green

    # but let's make it go around in circles:
    for i in range(500):
        angle = math.radians(i)  # increment in degrees
        rod.axis = (math.cos(angle), math.sin(angle), 0)
        rate(100)

def clock():  # no arguments here
    """
    two arrow objects, one going around more slowly,
    night happens

    note:  there's also a way to do rotation in XY
    by multiplying complex numbers, thanks to various
    identities (see orbits.py)
    """

    s = stage()
    s.autoscale = 0
    s.scale = (0.3, 0.3, 0.3)

    rod1 = arrow(pos=(0,0,0), axis=(3,0,0), shaftwidth=0.1)
    rod2 = arrow(pos=(0,0,0), axis=(1,0,0), shaftwidth=0.1)

    rod1.color = color.green
    rod2.color = color.red

    # clockwise this time, shorter one at 1/10th speed:
    for i in range(360*4,-1,-1):  # four circles of angle

        angle1 = math.radians(i)  # decrement in degrees
        angle2 = angle1/10.0

        if i == 360*2:  # switch to night view half way
            s.background = color.black

        rod1.axis = (3 * math.cos(angle1), 3 * math.sin(angle1), 0)
        rod2.axis = (1 * math.cos(angle2), 1 * math.sin(angle2), 0)
        rate(100)

def balls():  # no arguments here
    """
    arrow object leaves trail of balls

    """

    s = stage()
    s.autoscale = 0
    s.scale = (0.3, 0.3, 0.3)
    s.select()

    rod1 = arrow(pos=(0,0,0), axis=(3,0,0), shaftwidth=0.1)

    rod1.color = color.green

    # clockwise again
    for i in range(360,-1,-1):  # one circles of angle

        angle1 = math.radians(i)  # increment in degrees

        position = (3 * math.cos(angle1), 3 * math.sin(angle1), 0)
        rod1.axis = position

        ball = sphere(pos=position, radius=0.2)

        rate(100)

def spaceballs():  # no arguments here
    """
    arrow object leaves trail of balls, spaced by 10 degrees
    """

    s = stage()
    s.autoscale = 0
    s.scale = (0.3, 0.3, 0.3)

    rod1 = arrow(pos=(0,0,0), axis=(3,0,0), shaftwidth=0.1)

    rod1.color = color.green

    # clockwise again
    for i in range(360,-1,-1):  # one circles of angle

        angle1 = math.radians(i)  # increment in degrees

        position = (3 * math.cos(angle1), 3 * math.sin(angle1), 0)
        rod1.axis = position

        if not (i % 10):
            ball = sphere(pos=position, radius=0.2, color = color.orange)

        rate(100)

def rings():
    """
    Have a ball travel around on a ring
    """
    s = stage()
    s.autoscale = 0
    s.scale = (0.3, 0.3, 0.3)
    s.select()

    thering = ring(pos=(0,0,0), axis=(0,0,1),  # OK to comment this way
                   radius=2.5, thickness=0.1, color=color.green)

    theball = sphere(pos=(2.5,0,0), radius=0.2, color = color.orange)

    # clockwise again
    for i in range(360*5,-1,-1):  # five circles of angle

        angle1 = math.radians(i)  # increment in degrees

        position = (2.5 * math.cos(angle1), 2.5 * math.sin(angle1), 0)
        theball.pos = position

        rate(100)

def pyramids():
    """
    Desert plane, some Egyptian pyramids
    """
    s = stage()
    s.backcolor = color.blue  # dark blue sky
    s.autoscale = 0
    s.scale = (0.1, 0.1, 0.1)

    mybox = box(pos=(0,0,0), length=10, height=0.1, width=10,
                color = color.yellow)

    p1 = pyramid(pos=(0,0,0), axis = (0,1,0),
                 size=(4,2,2), color = color.red)

    p2 = pyramid(pos=(-4,0,-3), axis = (0,1,0),
                 size=(5,1,1), color = color.green)

    p3 = pyramid(pos=(2,0,4), axis = (0,1,0),
                 size=(6,2,2), color = color.orange)

if __name__ == '__main__':
    # firsttry()
    # clock()
    # balls()
    # spaceballs()
    # rings()
    pyramids()