Preserving aspect ratio in animation

asked 2015-03-30 23:34:56 +0200

Jeff Ford
41 ●6

updated 2015-03-31 03:24:44 +0200

kcrisman
12222 ●41 ●135 ●254

I'm trying to animate a series of increasing, nested tori. I'm testing the code for the first one, but the aspect ratio isn't behaving, and axes are showing up. I've tried messing with figsize, to no avail. Suggestions?

u,v = var('u,v')
def is_even(n):
    return n%2 == 0

def c(n):
   return 2/3*(4^(n+1)-4)

def torus(n,u,v):
   if is_even(n):
        return [(2*4**n + 4**n*cos(u))*cos(v), (2*4**n + 4**n*cos(u))*sin(v) + c(n), 4**n*sin(u)]
    else:
        return [4**n*sin(u), (2*4**n + 4**n*cos(u))*sin(v) + c(n),  (2*4**n + 4**n*cos(u))*cos(v)]

T = []

for i in range(10):
    T.append(parametric_plot3d(torus(0,u,v), (u,0,(i+1)*2*pi/9), (v,0,(i+1)*2*pi/9), axes="false"))

a = animate(T)
a.show()

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answered 2015-03-31 03:54:28 +0200

kcrisman
12222 ●41 ●135 ●254

I think part of your problem is that your bounds for the plots are not the same, but I'm not sure there is an easy way to make the bounds work that way in a parametric plot. Maybe you can pad it with an 'invisible' part?

However, putting aspect_ratio=1 in the plot command seems to help once the torus has worked its way around some of the way.

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answered 2015-03-31 22:35:36 +0200

Jeff Ford
41 ●6

I incorporated the suggestions and worked the bounds into two different loops. Seems to have fixed it.

u,v = var('u,v')

def is_even(n):
    return n%2 == 0

def c(n):
    return 2/3*(4^(n+1)-4)

def torus(n,u,v):
    if is_even(n):
        return [(2*4**n + 4**n*cos(u))*cos(v), (2*4**n + 4**n*cos(u))*sin(v)+c(n), 4**n*sin(u)]
    else:
        return [4**n*sin(u), (2*4**n + 4**n*cos(u))*sin(v)+c(n),  (2*4**n + 4**n*cos(u))*cos(v)]
T0 = []
for i in srange(0,2*pi+0.1, 0.1):
    T0.append(parametric_plot3d(torus(0,u,v), (u,0,2*pi),(v,i, i+0.1), aspect_ratio=1, frame=False, axes=False))

T = []    
for i in range(len(T0)):
    T.append(sum(T0[j] for j in range(i)))

a = animate(T)
a.show()

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answered 2015-03-31 22:26:01 +0200

eric_g
8209 ●10 ●61 ●162 https://luth.obspm.fr/...

updated 2015-03-31 22:32:24 +0200

To not depict the axes, you should use axes=False instead of axes="false". Also you may consider adding frame=False to suppress the bounding boxes. Taking into account kcrisman's suggestion aspect_ratio=1, you command should become

T.append(parametric_plot3d(torus(0,u,v), (u,0,(i+1)*2*pi/9), (v,0,(i+1)*2*pi/9), aspect_ratio=1, axes=False, frame=False))

However, there is still the issue that the bounds are not the same for each plot...

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