Pre-requisite:

Objectives:

To demonstrate an object launch to a target point

Advance:

Target Moving with Random factors

Descriptions:

To move your object towards a location,provided targeted location and current location, you can suppose your current location origin and then get the relative position of the target location in polar coordinate.
This will give you the direction you need to travel.
Given the speed you want the object to travel,
Simple example : (Please expand source to view. There's more example after this , please scroll down)
Simplest example
```
 
// x1, y1 are current position, x2, y2 are target position
float x1, y1, x2, y2;
 
void setup(){
	size(600,400);
	// Set current position to centre
	x1 = 300;
	y1 = 200;
}
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);
		if( y2 < y1 ){
			theta = 2 * PI - theta;
		}
		x1 += 2 * cos(theta);
		y1 += 2 * sin(theta);
	}
 
	// Draw the result
	ellipse( x1, y1, 30, 30 );
}
```
Stepped example : (Click mouse to step, Hold down to see the hint, More content under demo 1, please scroll down to view Keynote 0)
Source
```
 
//*******************************************************
// Global variables
//*******************************************************
final int appwidth = 600;
final int appheight = 600;
final float stepsize = 10;
targetedobject myobject;
//*******************************************************
// The class of the moving object
//*******************************************************
class targetedobject {  // This is the object to move
  int mcurrentx, mcurrenty;  // This will store the current location of the object
  int mtargetx, mtargety;    // This will store the target location of the object
  int mtargetx_t, mtargety_t;  // Step travel
  float mrotation;      // This is the current orientation of this object
  float thisstep;
  boolean demostep;		// The flag whether the helper needs to be displayed or not
  targetedobject( int x, int y, int r ) {  // Initialize with coordinate and orientation
    mcurrentx = x;
    mtargetx = x;
    mcurrenty = y;
    mtargety = y;
    mrotation = r;
    demostep = false;
  }
  void updatedraw() {  // Draws the shape
    pushMatrix();
    translate( mcurrentx, mcurrenty );
    rotate( mrotation );
    noStroke();
    fill( 255, 0, 0 );
    ellipse(0, 0, 40, 40);
    noFill();
    stroke(255);
    strokeWeight(5);
    line( -10, 0, 10, 0 );
    line( 10, 0, 5, -5 );
    line( 10, 0, 5, 5 );
    popMatrix();
    this.drawhelper();
  }
  void drawhelper() {
    if ( this.demostep ) {  // Need draw helper
      float textx, texty;
      noFill();
      strokeWeight(3);
      stroke( 0, 255, 255, 192 );
      line( this.mcurrentx, this.mcurrenty, this.mtargetx, this.mtargety );
      line( this.mtargetx, this.mcurrenty, this.mtargetx, this.mtargety );
      line( this.mcurrentx, this.mcurrenty, this.mtargetx, this.mcurrenty );
      textSize(24);
      textAlign(CENTER, BOTTOM);
      noStroke();
      fill(255);
      textx = (this.mtargetx + this.mcurrentx) / 2;
      texty = this.mcurrenty;
      text( "X2 - X1", textx, texty );
      textAlign(LEFT, CENTER);
      textx = this.mtargetx;
      texty = (this.mtargety + this.mcurrenty) / 2;
      text( "Y2 - Y1", textx, texty );
      textAlign(CENTER, CENTER);
      textx = (this.mtargetx + this.mcurrentx) / 2;
      texty = (this.mtargety + this.mcurrenty) / 2;
      text( "L", textx, texty );
      
      noFill();
      strokeWeight(3);
      stroke(255,0,0);
      arc( this.mcurrentx, this.mcurrenty, 64, 64, 0, this.mrotation );
      textx = this.mcurrentx + 40;
      texty = this.mcurrenty + 40;
      text( degrees(this.mrotation), textx, texty );
    }
  }
  void startstep(int x, int y) {
    float targetlength;
    float temprotation;
    this.demostep = true;
 
	// Remember target coordinates
    this.mtargetx = x;
    this.mtargety = y;
 
	// Calculate the distance between the endpoint and start point
    targetlength = sqrt( pow( this.mtargetx - this.mcurrentx, 2 ) + 
      					 pow(  this.mtargety - this.mcurrenty, 2 ) );  //Get the target distance
    if (targetlength <= 0.5) {
      this.mrotation = 0;
      return;  //Do not move
    }
    if (targetlength > stepsize) {  //Calculate step size
      this.thisstep = stepsize;
    }
    else {
      this.thisstep = targetlength;
    }
 
	// Get the direction (0~180 degree(s))
    temprotation = acos( (this.mtargetx - this.mcurrentx) / targetlength );
    if ( this.mtargety > this.mcurrenty ) {
      this.mrotation = temprotation;
    }else{
      this.mrotation = 2 * PI - temprotation;	// > 180 degrees
    }
    // Calculate the step target
    this.mtargetx_t = (int)(this.thisstep * cos(this.mrotation));
    this.mtargety_t = (int)(this.thisstep * sin(this.mrotation));
  }
  void endstep() {
    this.demostep = false;
	// Move the object
    this.mcurrentx += this.mtargetx_t;
    this.mcurrenty += this.mtargety_t;
  }
}
//*******************************************************
// Setup the size and the moving object
//*******************************************************
void setup() {
  size(appwidth, appheight);
  background(0);
  myobject = new targetedobject( width / 2, height / 2, 0 );
}
//*******************************************************
// Update the draw
//*******************************************************
void draw() {
  background(0);
  myobject.updatedraw();
}
//*******************************************************
// When mouse is pressed, start the stepping 
// Calculation process
//*******************************************************
void mousePressed() {
  if (mouseButton == LEFT) {
    myobject.startstep(mouseX, mouseY);
  }
}
//*******************************************************
// After the mouse is released,
// End the stepping and move the object
//*******************************************************
void mouseReleased() {
  if ( myobject.demostep ) {
    myobject.endstep();
  }
}
```
Key note
```
 
//Get the target distance
targetlength = sqrt( pow( this.mtargetx - this.mcurrentx, 2 ) + 
                     pow( this.mtargety - this.mcurrenty, 2 ) );
 
//Arc cosin adjacent side divide by Hypotenuse
//OR arc sin subtense divide by Hypotenuse
//Not using tangent to avoid Divide by Zero
temprotation = acos( (this.mtargetx - this.mcurrentx) / targetlength );
 
//In this case, we are using cosin, so for the angle > 180 which means that
//targety is under currend y
if ( this.mtargety > this.mcurrenty ) {  //> 180 degrees
    this.mrotation = temprotation;
}else{
    this.mrotation = 2 * PI - temprotation;
}
 
//Now that we have the rotation, we recalculate the x and y we need to travel
this.mtargetx_t = (int)(this.thisstep * cos(this.mrotation));
this.mtargety_t = (int)(this.thisstep * sin(this.mrotation));

 
//Finally, move the object
this.mcurrentx += this.mtargetx_t;
this.mcurrenty += this.mtargety_t;
```
Continuous Example ( jitter is actually due to the fps not being stable )
Source
```
 
final float appwidth = 600;
final float appheight = 600;
final float stepsize = 5;
targetedobject myobject;
class targetedobject {  // This is the object to move
  float mcurrentx, mcurrenty;  // This will store the current location of the object
  float mtargetx, mtargety;    // This will store the target location of the object
  float mtargetx_t, mtargety_t;  // Step travel
  float mrotation;      // This is the current orientation of this object
  float thisstep;
  boolean demostep;
  targetedobject( float x, float y, float r ) {  // Initialize with coordinate and orientation
    mcurrentx = x;
    mtargetx = x;
    mcurrenty = y;
    mtargety = y;
    mrotation = r;
    demostep = false;
  }
  void updatedraw() {  //Draws the shape
    pushMatrix();
    translate( mcurrentx, mcurrenty );
    rotate( mrotation );
    noStroke();
    fill( 255, 0, 0 );
    ellipse(0, 0, 40, 40);
    noFill();
    stroke(255);
    strokeWeight(5);
    line( -10, 0, 10, 0 );
    line( 10, 0, 5, -5 );
    line( 10, 0, 5, 5 );
    popMatrix();
  }
  void moveto(float x, float y) {
    this.mtargetx = x;
    this.mtargety = y;
    //Get the target distance
    float targetlength = sqrt( pow( this.mtargetx - this.mcurrentx, 2 ) + 
      pow( this.mtargety - this.mcurrenty, 2 ) );
    if(targetlength < 0.5){
      return;
    }
    //Arc cosin adjacent side divide by Hypotenuse
    //OR arc sin subtense divide by Hypotenuse
    //Not using tangent to avoid Divide by Zero
    float temprotation = acos( (this.mtargetx - this.mcurrentx) / targetlength );
    //In this case, we are using cosin, so for the angle > 180 which means that
    //targety is under currend y
    if ( this.mtargety > this.mcurrenty ) {  //> 180 degrees
      this.mrotation = temprotation;
    }
    else {
      this.mrotation = 2 * PI - temprotation;
    }
    if (targetlength > stepsize) {  //Calculate step size
      this.thisstep = stepsize;
    }
    else {
      this.thisstep = targetlength;
    }
    //Now that we have the rotation, we recalculate the x and y we need to travel
    this.mtargetx_t = (int)(this.thisstep * cos(this.mrotation));
    this.mtargety_t = (int)(this.thisstep * sin(this.mrotation));

    //Finally, move the object
    this.mcurrentx += this.mtargetx_t;
    this.mcurrenty += this.mtargety_t;
  }
}
void setup() {
  size(appwidth, appheight);
  background(0);
  myobject = new targetedobject( width / 2, height / 2, 0 );
  frameRate(30);
}
void draw() {
  background(0);
  myobject.moveto( mouseX, mouseY );
  myobject.updatedraw();
}
```

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Pre-requisite:

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Descriptions:

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Targeted moving

Pre-requisite:

Objectives:

Advance:

Descriptions: