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Index › Programming Questions & Help › Programs › noise function
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noise function (Read 689 times)
oceanos
noise function
Dec 25th, 2009, 4:37pm  
Hi. I have a question. I want to use the noise function to affect a radial gradient. But the problem is that the zero angle does not have the same value as the 2 PI, so there is "flaw" in the gradient. Does the noise function have a period of some kind, that I can use as scale ? When I plot the perlin noise in 2D I can see repetitions, but I could not find the period...
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antiplastik
Re: noise function
Reply #1 - Dec 26th, 2009, 1:32am  
You need a noise function that returns the same value for 0 and TWO_PI, right? Like cos() or sin() maybe?

Why not something like that :
Code:
float a = 0.0;
for (float x = 0; x < width; x ++) {
  a += 0.01;
  float y = 20*cos(x*0.2)*noise(a);
  point(x, 50 + y);
}

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oceanos
Re: noise function
Reply #2 - Dec 26th, 2009, 9:51am  
Hi. Thanks for your response. I can see that I was not completly clear in my previous post. I'm goin to try to explain a little bit more. The problem with the cos() and sin() is that they repeat values between O and TWO_PI, and they give very symmetric results (-1,1). I want something that only repeat itself with a TWO_PI period.

To give a little bit more context. This is the example that I'm talking about. openprocessing.org/visuals/?visualID=6684

The sun corona looks very symmetric and not natural, because I could not think of function that only repeat itself with TWO_PI period.

Code:

float d = a > PI ? TWO_PI - a : a; 
float value = noise(x*0.05f,y*0.05f,d+timeStep)-start;


The d value should be something that only repeat itself with TWO_PI period. When I plot the noise function in 2D I can see some patterns repeating, so I imagine that the noise function has an internal period of some kind, but I dont know what that is.
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