the evil cube

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the evil cube

Postby luishp » Fri May 23, 2014 9:58 pm

Hi guys,

I am currently reading Introduction to Python Programming by John Zelle. I have gotten to the chapter about simulations and finished all the practice problems except one. This is the problem:

(Advanced) Here is a puzzle problem that can be solved with either some fancy analytic geometry (calculus) or a (relatively) simple simulation. Suppose you are located at the exact center of a cube. If you could look all around you in every direction, each wall of the cube would occupy 1/6 of your field of vision. Suppose you move toward one of the walls so that you are now half-way between it and the center of the cube. What fraction of your
field of vision is now taken up by the closest wall? Hint: use a Monte Carlo simulation that repeatedly “looks” in a random direction and counts how many times it sees the wall.


I would normally provide code along with this of what I have done but it's proven hard for me to even tackle this problem. I thought of how it would be done for a square instead of a cube.
# i would import math
# i would center a square of length 1 at (0, 0)
# i would make a point at (0, .5)
# from that point I would use
Code: Select all
angle = random() * 2 * math.pi

# Make a line going in the direction of the angle
# x = x + cos(angle)
y = y + sin(angle)
# and figure out which side of the square it intersects and record it

I'm not sure what exactly to do for a cube which is three dimensional. I'd really appreciate some direction.
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Re: the evil cube

Postby mckryall » Mon May 26, 2014 10:29 pm

I think this forum is mainly for language-specific questions. I'd recommend going to a computer science or physics forum. The physicists could probably help you with the math, and the computer scientists could probably help you understand what they said from a programming perspective. If the people at Stack Overflow's forums don't go flag-happy on yo' question, you might be able to use that as a last resort. Come back to us when you have questions about getting this to work in python specifically. Good luck.
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Re: the evil cube

Postby Kebap » Tue May 27, 2014 10:14 am

Hi luishp,

I like your idea of starting with 2d, then figuring out 3d solutions later. However, I would not use a random angle in 2d, as you are right, this is hard to copy to 3d.

Why don't you try using 2 random numbers, one for x dimension, one for y dimension. Then you can later add a random z dimension value, and be done with it (almost) :mrgreen:
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