Image: Animated construction of Sierpinski Triangle

Description: Animated construction of Sierpinski Triangle Self-made. Licensing I made this with SAGE, an open-source math package. The latest source code lives here, and has a few better variable names & at least one small bug fix than the below. Others have requested source code for images I generated, below. Code is en:GPL; the exact code used to generate this image follows: #***************************************************************************** # Copyright (C) 2008 Dean Moore < dean dot moore at deanlm dot com > # < deanlorenmoore@gmail.com > # # # Distributed under the terms of the GNU General Public License (GPL) # http://www.gnu.org/licenses/ #***************************************************************************** ################################################################################# # # # Animated Sierpinski Triangle. # # # # Source code written by Dean Moore, March, 2008, open source GPL (above), # # source code open to the universe. # # # # Code animates construction of a Sierpinski Triangle. # # # # See any reference on the Sierpinski Triangle, e.g., Wikipedia at # # < http://en.wikipedia.org/wiki/Sierpinski_triangle >; countless others are # # out there. # # # # Other info: # # # # Written in sage mathematical package sage (http://www.sagemath.org/), hence # # heavily using computer language Python (http://www.python.org/). # # # # Important algorithm note: # # # # This code does not use recursion. # # # # More topmatter & documentation probably irrelevant to most: # # # # Inspiration: I viewed it an interesting problem, to try to do an animated # # construction of a Sierpinski Triangle in sage. Thought I'd be lazy & search # # the 'Net for open-source versions of this I could simply convert to sage, but # # the open-source code I found was poorly documented & I couldn't figure it # # out, so I gave up & solved the problem from scratch. # # # # Also, I wanted to animate the construction, which I did not find in # # open-source code on the 'Net. # # # # Comments on algorithm: # # # # The code I found on the 'Net was recursive. I do not much like recursion, # # considering it way for programmers to say, "Look how smart I am! I'm using # # recursion! Aren't I cool?!" I feel strongly recursion is often confusing, # # can chew up too much memory, and should be avoided except when # # # # a) It's unavoidable, or # # b) The code would be atrocious without it. # # # # Did some thinking & swearing, but concocted a non-recursive method, and by # # doing the problem from scratch. Guess it avoids all charges of copyright # # violation, plagiarism, whatever. # # # # More on algorithm via ASCII art. Below we have a given triangle, shaded via # # x's. # # # # The next "generation" is the blank triangles. Sit down & start a Sierpinski # # Triangle on scratch: the next generation is always two on each side of a # # given triangle from the last generation, one on top. Algorithm takes the # # given, shaded triangle (below), and makes the three of the next generation # # arising from it. # # # # See code for more on how this works. # # __________ # # \ / # # \ / # # \ / # # \ / # # _________\/_________ # # \ xxxxxxxxxxxxxxxx / # # \ xxxxxxxxxxxxxx / # # \ xxxxxxxxxxxx / # # \ xxxxxxxxxx / # # _________\ xxxxxxxx /_________ # # \ /\ xxxxxx /\ / # # \ / \ xxxx / \ / # # \ / \ xx / \ / # # \ / \ / \ / # # \/ \/ \/ # # # ################################################################################# # # # Begin program: # # # # First we need three functions; see the below code on how they are used. # # # # The three functions *right_side_triangle* , *left_side_triangle* & # # *top_triangle* are here defined & not as "lambda" functions, as they need # # documented. # # # # I don't care to replicate the poorly-documented code I found on the 'Net. # # # ################################################################################# # # # First function, *right_side_triangle*. # # # # Function *right_side_triangle* gives coordinates of next triangle on right # # side of a given triangle whose coordinates are passed in. # # # # Points *p*, *r*, *q*, *s* & *t* are labeled as passed in: # # # # (p, r)____________________(q, r) # # \ / # # \ / # # \ / # # \ / # # \ (p1, r1)/_________ (q1, r1) # # \ /\ / # # \ / \ / # # \ / \ / # # \ / \ / # # \/ \/ # # (s, t) (s1, t1) # # # # p1 = (q + s)/2, a simple average. # # q1 = q + (q - s)/2 = (3*q - s)/2 # # r1 = (r + t)/2, a simple average. # # s1 = q, easy. # # t1 = t, easy. # # # ################################################################################# def right_side_triangle(p,q,r,s,t): p1 = (q + s)/2 q1 = (3*q - s)/2 r1 = (r + t)/2 s1 = q # A placeholder, solely to make code clear. t1 = t # Ditto, a placeholder. return ((p1,r1),(q1, r1),(s1, t1)) # End of function *right_side_triangle*. ################################################################################# # # # Function *left_side_triangle*: # # # # (p, q) ____________________(q, r) # # \ / # # \ / # # \ / # # \ / # # (p1, r1) _________\ (q1, r1) / # # \ /\ / # # \ / \ / # # \ / \ / # # \ / \ / # # \/ \/ # # (s1, t1) (s, t) # # # # p1 = p - (s - p)/2 = (2p-s+p)/2 = (3p - s)/2 # # q1 = (p + s)/2, a simple average # # r1 = (r + t)/2, a simple average. # # s1 = p, easy. # # t1 = t, easy. # # # ################################################################################# def left_side_triangle(p,q,r,s,t): p1 = (3*p - s)/2 q1 = (p + s)/2 r1 = (r + t)/2 s1 = p # A placeholder, solely to make code clear. t1 = t # Ditto, a placeholder. return ((p1,r1),(q1, r1),(s1, t1)) # End of function *left_side_triangle*. ################################################################################# # # # Function *top_triangle*. # # # # (p1, r1) __________ (q1, r1) # # \ / # # \ / # # \ / # # \ / (s1, t1) # # (p, r)_________\/_________ # # \ xxxxxxxxxxxxxxxx / # # \ xxxxxxxxxxxxxx / (q, r) # # \ xxxxxxxxxxxx / # # \ xxxxxxxxxx / # # \ xxxxxxxx / # # \ xxxxxx / # # \ xxxx / # # \ xx / # # \ / # # \/ # # (s, t) # # # # p1 = (p + s)/2, a simple average. # # q1 = (s + q)/2, a simple average # # r1 = r + (r - t)/2 = (3r - t)/2 # # s1 = s, easy. # # t1 = r, easy. # # # ################################################################################# def top_triangle(p,q,r,s,t): p1 = (p + s)/2 q1 = (s + q)/2 r1 = (3*r - t)/2 s1 = s # Again, both this & next are t1 = r # placeholders, solely to make code clear. return ((p1,r1),(q1, r1),(s1, t1)) # End of function *top_triangle*. ################################################################################# # # # Main program commences: # # # ################################################################################# # Top matter a user may wish to vary: number_of_generations = 8 # How "deep" goes the animation after initial triangle. first_triangle_color = (1,0,0) # First triangle's rgb color as red-green-blue tuple. chopped_piece_color = (0,0,0) # Color of "chopped" pieces as rgb tuple. delay_between_frames = 50 # Time between "frames" of final "movie." figure_size = 12 # Regulates size of final image. initial_edge_length = 3^7 # Initial edge length. # End of material user may realistically vary. Rest should churn without user input. number_of_triangles_in_last_generation = 3^number_of_generations # Always a power of three. images = [] # Holds images of final "movie." coordinates = [] # Holds coordinates. p0 = (0,0) # Initial points to start iteration -- note p1 = (initial_edge_length, 0) # y-values of *p0* & *p1* are the same -- an p2 = ((p0[0] + p1[0])/2, # important book-keeping device. ((initial_edge_length/2)*sin(pi/3))) # Equilateral triangle; see any Internet # reference on these. # We make a polygon (triangle) of initial points: this_generations_image = polygon((p0, p1, p2), rgbcolor=first_triangle_color) images.append(this_generations_image) # Save image from last line. coordinates = [( ( (p0[0] + p2[0])/2, (p0[1] + p2[1])/2 ), # Coordinates ( (p1[0] + p2[0])/2, (p1[1] + p2[1])/2 ), # of second ( (p0[0] + p1[0])/2, (p0[1] + p1[1])/2 ) )] # triangle. # It is *supremely* important # that the y-values of the first two # points are equal -- check definitions # above & code below. this_generations_image = polygon(coordinates[0], # Image of second triangle. rgbcolor=chopped_piece_color) images.append(images[0] + this_generations_image) # Save second image, tacked on top of first. # Now the loop that makes the images: number_of_triangles_in_this_generation = 1 # We have made one "chopped" triangle, the second, above. while number_of_triangles_in_this_generation < number_of_triangles_in_last_generation: this_generations_image = Graphics() # Holds next generation's image, initialize. next_generations_coordinates = [] # Holds next generation's coordinates, set to null. for a,b,c in coordinates: # Loop on all triangles. (p, r) = a # Right point; note y-value of this & next are equal. (q, r1) = b # Left point; note r1 = r & thus *r1* is irrelevant; # it's only there for book-keeping. (s, t) = c # Bottom point. # Now construct the three triangles & their three polygons of the next # generation. right_triangle = right_side_triangle(p,q,r,s,t) # Here use those left_triangle = left_side_triangle (p,q,r,s,t) # utility functions upper_triangle = top_triangle (p,q,r,s,t) # defined at top. right = polygon(right_triangle, rgbcolor=(chopped_piece_color)) # Make next left = polygon(left_triangle, rgbcolor=(chopped_piece_color)) # generation's top = polygon(upper_triangle, rgbcolor=(chopped_piece_color)) # triangles. this_generations_image = this_generations_image + (right + left + top) # Add image. next_generations_coordinates.append(right_triangle) # Save the coordinates next_generations_coordinates.append( left_triangle) # of triangles of the next_generations_coordinates.append(upper_triangle) # next generation. # End of "for a,b,c" loop. coordinates = next_generations_coordinates # Save for next generation. images.append(images[-1] + this_generations_image) # Make next image: all previous # images plus latest on top. number_of_triangles_in_this_generation *= 3 # Bump up. # End of *while* loop. a = animate(images, figsize=[figure_size, figure_size], axes=False) # Make image, ... a.show(delay = delay_between_frames) # Show image. # End of program. End of code.
Title: Animated construction of Sierpinski Triangle
Credit: Own work (Original text: self-made)
Author: Dino at English Wikipedia (Original text: dino (talk))
Usage Terms: Creative Commons Attribution-Share Alike 3.0
License: CC BY-SA 3.0
License Link: http://creativecommons.org/licenses/by-sa/3.0
Attribution Required?: Yes