Need help, my first program

Klop

Fractal Newbie

Posts: 3

« on: April 28, 2007, 12:52:15 AM »

Hi everybody, I'm new here and I have a question :p

I'm making my very first fractal generation program for university, the problem is that nothing was taught to us about fractals except that the method we're using is the following (I'm using Java):

1. We have an initiator which is the initial Polygon (a vector of Points that connects the last to the first).
2. We have a generator which is a Polyline (a vector of Points that doesn't connect the last to the first) that replaces each of the initiator's vertices every time the function next() is called.

The only problem I'm having is with the scaling, rotating and translating of the generator so that each generator can replace each vertex of the initiator. If hope someone can help me with that. Thanks in advance.

PS: Keep in mind that the generator can be of any size and so can be any of the vertices of the initiator.


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lycium

Fractal Bachius

Posts: 519

Re: Need help, my first program

« Reply #1 on: April 28, 2007, 01:16:34 AM »

your problem description is pretty light on details (read: there are no details Tongue

), however i have recently had a similar university assignment. we were required to produce a koch "snowflake" fractal, and i can immediately refer you to my online solution: http://www.fractographer.com/cos340/cos340-a%20ass1.pdf (it's question 4)

the solution i used there is based on l-systems, which is a bit easier than using a recursive approach -- which is, i guess, why you were given that question in the first place! Wink

to further complicate the matter, my code is definitely not what you want to be reading if you've just started writing your first programs...

so, assuming you're familiar with vector arithmetic, you just need to keep making a new list of vertices which grows by a constant factor relative to the last each iteration. each line gets replaced with several new ones, in my case 4, so you'd be adding 3 new vertices (it's 3am, this is off the top of my head, so double checking my spam might be good) each iteration. with a scale factor of sqrt(3) you offset the middle of each edge along its normal direction (if the edge vector is <dx,dy> then the normal is +/- <-dy,dx>) and link that up to the beginning and end segments.

hope that helps! the coding itself is the hard part of course, but it's what you're there to learn mate Wink


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http://lyc.deviantart.com

Klop

Fractal Newbie

Posts: 3

Re: Need help, my first program

« Reply #2 on: April 28, 2007, 03:52:09 AM »

Thanks for your help, I contacted a teacher though and he explained it to me, I made a mistake there, I meant replacing each segment by the generator and not each vertex Tongue

Anyways, I figured it out. first I find the length of the segment and the distance between the extremes of the generator and then I scale the generator (its clone, I don't want to modify the original) by (segment_length/generator_distance_extremes) so that the distance between the extremes of the generator becomes the same as the length of the segment.
Then I translate the generator so that it's first Point matches the first Point of the segment.
And finally I move both the first Point of the segment and the first Point of the generator to the origin (after storing the Point where they were), rotate them by alpha - beta (being alpha the angle of the second Point of the segment and beta the angle of the last Point of the generator), and then move them back.
This way the generator matches the segment, then all I have to do is replace it Tongue

I'll bring screenshots later xD


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Nahee_Enterprises

Fractal Bachius

Posts: 536

Re: Need help, my first program

« Reply #3 on: April 28, 2007, 11:19:24 AM »

Klop wrote:
>
> Hi everybody, I'm new here...
> I'm making my very first fractal generation program for university.....
> ..... I'll bring screenshots later....

Greetings!! And welcome to this Forum.

Look forward to seeing how your images turn out on your assignment.


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Sincerely,
P.N.L.
-------------------------------------------------
http://home.att.net/~Paul.N.Lee/PNL_Fractals.html
http://www.Nahee.com/Fractals/

Klop

Fractal Newbie

Posts: 3

Re: Need help, my first program

« Reply #4 on: April 29, 2007, 02:45:43 AM »

Thanks

Here they are:
http://i168.photobucket.com/albums/u167/jmorais24000/[XX].png

where [XX] is any number between 1 and 20. I'll bring colored ones later :p

EDIT:
Now the numbers go up to 23, numbers 22 and 23 are colored ones


« Last Edit: April 30, 2007, 02:59:09 AM by Klop »	Logged

Nahee_Enterprises

Fractal Bachius

Posts: 536

Re: Need help, my first program

« Reply #5 on: April 30, 2007, 09:49:00 PM »

Have not looked at all of your plots yet (I started at # 23 and began working backwards). I found # 21 interesting to see a Julia like spiral appearing in the density of the triangles. The pattern of # 17 I also found interesting.

Keep us informed on your progress and any interesting images that you create. And if you have questions, just post them to this forum.


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Sincerely,
P.N.L.
-------------------------------------------------
http://home.att.net/~Paul.N.Lee/PNL_Fractals.html
http://www.Nahee.com/Fractals/

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