Pre-requisite:

1. Polar and Cartesian Coordinates

Objectives:

1. To demonstrate an object launch to a target point

Descriptions:

1. 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.
2. This will give you the direction you need to travel.
3. Given the speed you want the object to travel,

4. Stepped example : (Click mouse to step, Hold down to see the hint, More content under demo 1, please scroll down)

   Source

    
   final int appwidth = 600;
   final int appheight = 600;
   final float stepsize = 10;
   targetedobject myobject;
   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;
     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
         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 );
       }
     }
     void startstep(int x, int y) {
       float targetlength;
       float temprotation;
       this.demostep = true;
       this.mtargetx = x;
       this.mtargety = y;
       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;
       }
       temprotation = acos( (this.mtargetx - this.mcurrentx) / targetlength );
       if ( this.mtargety > this.mcurrentx ) {  //> 180 degrees
         this.mrotation = temprotation;
       }else{
         this.mrotation = 2 * PI - temprotation;
       }
       // 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;
       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 );
   }
   void draw() {
     background(0);
     myobject.updatedraw();
   }
   void mousePressed() {
     if (mouseButton == LEFT) {
       myobject.startstep(mouseX, mouseY);
     }
   }
   void mouseReleased() {
     if ( myobject.demostep ) {
       myobject.endstep();
     }
   }
   

5. Essential Code explaination