引っかき傷

/**
* scratch
*
* @author aa_debceb
* @date 2016/03/11
*/

float margin = 50;
float base;
float baseStep = 1.3;
float y[];
float gray;
float gStep = 0.3;

void setup(){
  size(640, 640);
  
  strokeWeight(1);
  background(255);
  
  gray = 0;
  base = 0;
  y = new float[width];
  for(int i = 0; i < width; i++){
    y[i] = 0;
  }
}

void draw(){
  
  stroke(gray);
  beginShape();
  for(int i = 0; i < width; i++){
    vertex(i, base + y[i]);
  }
  endShape();
  
  for(int i = 0; i < width; i++){
    y[i] += map(random(1), 0, 1, -0.3, 0.3);
  }
  
  base += 1;
  if(base > height + margin){
    base = -margin;
  }
  
  gray += gStep;
  if(gray > 255){
    gStep *= -1;
  } else if(gray < 0){
    gStep *= -1;
  }

}