[VPython] Animations

Animations

 

Moving Graphs에서 볼 수 있듯이, Animations의 핵심은 일정 시간 동안 동작을 수행할 수 있는 rate(#)이다.

 

animation이 무한 재생되도록 하려면 (while True:) loop를 사용하고,  (for i in range(#):) loop는 finite 시간 동안 재생한다.

 

참고 : 프로그램이 고장나면 loop에 rate(#)가 있는지 확인.

 

Bouncing Ball Example

 

# make sphere and 2 wall objects
my_sphere = sphere(pos=vector(0,0,0), radius=0.25, color=color.green )
wall1 = box(pos=vector(2,0,0), size=vector(0.1,1,1), color=color.white)
wall2 = box(pos=vector(-2,0,0), size=vector(0.1,1,1), color=color.white)
# define the inner edge that ball hits
edge1 = wall1.pos.x - wall1.size.x/2
edge2 = wall2.pos.x - wall2.size.x/2
# while loop does the animation
dx = 0.01 # dx is distance ball moves for each loop
while True:
 rate(100) # delay between each loop
 if (my_sphere.pos.x + my_sphere.radius >= edge1) or
 (my_sphere.pos.x – my_sphere.radius <= edge2):
 	dx = -dx # if sphere at wall, reverse direction
 my_sphere.pos.x = my_sphere.pos.x+dx # move sphere’s x position by dx

 

한정된 시간 동안 animation을 실행하려면(ex. 100 loops) (while True:) loop를 replace한다.

 

for i in range(100):

 

Animation with Moving Graph Example

 

# create sphere object
my_sphere = sphere(pos=vector(1,0,0), size=vector(0.5,0.5,0.5))
# create graph
g = graph(scroll=True, xmin=0, xmax=10)
x_plot = gcurve(graph=g, color=color.red, label="x")
y_plot = gcurve(graph=g, color=color.green, label="y")
# animation
time = 0
while True:
 rate(100)
 # move sphere x an y using cos and sin
 my_sphere.pos.x = cos(time)
 my_sphere.pos.y = sin(time)
 # plot new x and y
 x_plot.plot(time,cos(time))
 y_plot.plot(time,sin(time))
 time += 0.01 # increase time by 0.01

 

Rotating Gear Example – Animating 2D Shapes

 

# create gear shape
g = shapes.gear(n=20)
gear1 = extrusion(path=[vector(0,0,0), vector(0,0,0.1)],
 shape=g, pos=vector(2,0,0))
gear2 = extrusion(path=[vector(0,0,0), vector(0,0,0.1)],
 shape=g, pos=vector(0,0,0))
# rotate gear animation
gear1.rotate(axis=vector(0,0,1), angle=0.1)
while True:
 rate(10)
 gear1.rotate(axis=vector(0,0,1), angle=0.05) # rotate CCW
 gear2.rotate(axis=vector(0,0,1), angle=-0.05) # rotate CW