from visual import *
# demonstration of vector cross product
print """
Vector cross product: Red cross Green = Yellow
Drag to change green vector
Click to toggle fixed angle or fixed length
"""
# Ruth Chabay
scene.title="Vector Cross Product"
scene.width=600
scene.height=600
R = 0.15*4
plane = curve(pos=[(0, -10, -10), (0, -10, 10), (0, 10,10), (0, 10, -10),
(0, -10, -10), (0,-6,-10), (0,-6,10), (0, -2, 10), (0, -2, -10),
(0,2,-10), (0,2,10), (0,6,10), (0,6,-10),(0,10, -10),
(0,10,-6), (0,-10,-6), (0,-10,-2), (0,10,-2), (0,10,2),
(0,-10,2), (0,-10,6), (0,10,6)])
s_theta=sphere(pos=(0,-12,-10), radius=0.6, color=(0.6, 1.0, 0.6))
s_theta_label=label(pos=s_theta.pos, text="Fix Angle", yoffset=-5,
opacity=0, box=0, line=0)
s_length=sphere(pos=(0,-12,10), radius=0.6, color=(0.6, 0.6, 1.0))
s_length_label=label(pos=s_length.pos, text="Fix Length", yoffset=-5,
opacity=0, box=0, line=0)
s_text=label(pos=(0,12,0), text="Yellow = Red x Green",
opacity=0, box=0, line=0)
fixlength = 0
fixtheta = 0
avector = array ([0,0,-3.5])
bvector = vector (0,3,2)
a = arrow(pos=(0,0,0), shaftwidth=R, color=crayola.red)
b = arrow(pos=(0,0,0), axis=bvector, shaftwidth=R, color=crayola.green)
a.axis =avector
cvector = cross(avector,bvector)
c = arrow(pos=(0,0,0), axis=cvector, shaftwidth=R, color=crayola.yellow)
scene.autoscale = 0
scene.forward = (-1,-.5,-1)
drag = 0
while True:
rate(100)
if scene.mouse.events:
m = scene.mouse.getevent()
if m.drag:
drag = True
obs = None
elif m.drop:
drag = False
elif m.click:
if m.pick is s_length:
if fixtheta:
fixtheta = not(fixtheta)
s_theta.color = (0.6, 1.0, 0.6)
fixlength=not(fixlength)
if fixlength:
s_length.color=(0.0, 0.0, 1.0)
else:
s_length.color=(0.6, 0.6, 1.0)
elif m.pick is s_theta:
if fixlength:
fixlength = not(fixlength)
s_length.color=(0.6, 0.6, 1.0)
fixtheta = not(fixtheta)
if fixtheta:
s_theta.color=(0.0, 1.0, 0.0)
else:
s_theta.color = (0.6, 1.0, 0.6)
if drag:
rate(100)
newobs=scene.mouse.project(normal=vector(1,0,0), d=0)
if newobs and (newobs != obs):
obs = newobs
if not fixlength and not fixtheta:
bvector = obs
if bvector.mag > 20: bvector=bvector*(20/bvector.mag)
b.axis=bvector
elif fixlength:
length=3.9
bvector = length*norm(obs)
b.axis=bvector
elif fixtheta:
length=mag(obs)
bvector=length*norm(vector(0, .3, 1))
b.axis=bvector
cvector=cross(avector,b.axis)
c.axis=cvector
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