Pre-requisite:

1. Targeted moving

Objectives:

1. Add some random factors to chasing the target
2. The movement may look jitter or shaky.

Advance:

1. Move along pre-calculated spline.

Descriptions:

1. Assume you can move the object to the target

2. Adding a random number to the theta will give you a more organic movement

   Source

    
   // x1, y1 are current position, x2, y2 are target positionfloat x1, y1, x2, y2;
     
   void setup(){
       size(600,400);
       // Set current position to centre
       x1 = 300;
       y1 = 200;
   	frameRate(30);
    
   	// Set the random seed so that the sequence is different each time
   	randomSeed(millis());
   }
   void draw(){
       background(0);
       fill(255);
       // Movement code here :
       x2 = mouseX;
       y2 = mouseY;
     
       float l = sqrt( pow((x2-x1),2) + pow((y2-y1),2) );
       if( l > 0.5 ){
           float theta = acos((x2-x1) / l);
   
   		// Add the random factor here
   		// The maths in processing is calculated in radians
   		// Gives it a +- 90 degrees of deviation
   		theta += radians( random( -90, 90 ) );
   
           if( y2 < y1 ){
               theta = 2 * PI - theta;
           }
           x1 += 2 * cos(theta);
           y1 += 2 * sin(theta);
       }
     
       // Draw the result
       ellipse( x1, y1, 30, 30 );
   }
   

3. Smoothing out the movement ( You don't want to change the direction each frame so it looks jumpy )

   Source

    
    // 10 frames to change a deviation
   final int deviationframe = 10;
   int framecount = 0;
    
   // Add a global to save the random factor
   float randangle = 0;
    
   // x1, y1 are current position, x2, y2 are target positionfloat x1, y1, x2, y2;
   float x1,y1,x2,y2;
     
   void setup(){
       size(600,400);
       // Set current position to centre
       x1 = 300;
       y1 = 200;
   	frameRate(30);
    
   	// Set the random seed so that the sequence is different each time
   	randomSeed(millis());
   }
   void draw(){
       background(0);
       fill(255);
       // Movement code here :
       x2 = mouseX;
       y2 = mouseY;
     
       float l = sqrt( pow((x2-x1),2) + pow((y2-y1),2) );
       if( l > 0.5 ){
           float theta = acos((x2-x1) / l);
   
   		// Add the random factor here
   		// The maths in processing is calculated in radians
   		// Gives it a +- 90 degrees of deviation
   		// Save the angle
   		
   		if( ++framecount > deviationframe ){
   			randangle = radians( random( -90, 90 ) );
   			framecount = 0;
   		}
   		theta += randangle;
   
           if( y2 < y1 ){
               theta = 2 * PI - theta;
           }
           x1 += 2 * cos(theta);
           y1 += 2 * sin(theta);
       }
     
       // Draw the result
       ellipse( x1, y1, 30, 30 );
   }