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Index › Programming Questions & Help › Syntax Questions › interpolating arrays
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interpolating arrays (Read 617 times)
sebastiano
interpolating arrays
Aug 6th, 2009, 11:11am  
hello i have 2 array with values, for example a = [2 , 5 , 7 , 4]   and

b = [ 4 , 6 , 7 , 2]

i need to change the values of my array a to b, but i need make with  interpolation, so the values of my array a converts to the values of my array b not suddenly but in a smoothly way.

is there an easy way of doing this?

thanksss
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koogy
Re: interpolating arrays
Reply #1 - Aug 6th, 2009, 1:53pm  
you need to know how many steps between the two positions.

then you'll need an array of increments where i[n] = (b[n] - a[n]) / num_steps. (actually, you can re-use b[] for the increments). (be careful when dividing integers, the answers need to be floats or doubles.)

then, each time through the loop, add i[n] to a[n].

there's also lerp() but i don't see any advantage over the above in this case.

http://processing.org/reference/lerp_.html
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sebastiano
Re: interpolating arrays
Reply #2 - Aug 8th, 2009, 1:54pm  
hi i made this code , but its not working, any idea of what am i doing wrong?

thanks
Code:



float[] a;
float[] b;
float[] incremento;

float num_steps;


void setup(){
  size(500, 500 );
  smooth();
  
  a = new float[20];
  b = new float[20];
  incremento = new float[20];
  

  num_steps = 5;
  for (int i = 0 ; i < 20 ; i ++) {
    a[i] = random(200);
    incremento[i] = a[i];
    b[i] = random(200);
    
  }
}


void draw(){
  background(250, 0, 0);
  if (keyPressed == true) {
    interpolate_array();
  }
  for (int i = 0 ; i < 20 ; i ++) {
    ellipse( incremento[i] , 20 , 30, 30);
    //print(" " + i + " " +  incremento[i]);
  }
}


void interpolate_array(){
 for (int i = 0 ; i < 20 ; i ++) {
 incremento[i] = (b[i] - a[i]  ) / num_steps;
 }
 
 }


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PhiLho 
Re: interpolating arrays
Reply #3 - Aug 8th, 2009, 2:39pm  
incremento, as the name implies, is supposed to hold the increment value, not the drawing values.
Possible change:
Code:
// [...]
  num_steps = 5;
  for (int i = 0 ; i < a.length ; i ++) {
    a[i] = random(200);
    b[i] = random(200);
    incremento[i] = (b[i] - a[i]) / num_steps;
  }
}


void draw(){
  background(250, 0, 0);
  if (keyPressed == true) {
    for (int i = 0 ; i < a.length ; i ++) {
	a[i] += incremento[i];
    }
  }
  for (int i = 0 ; i < a.length ; i ++) {
    ellipse(a[i] , 20 , 30, 30);
  }
}
(untested)
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