// By Chris Orban and Mark Schillaci for Physics 1251 at OSU Marion

float x;
float y;

float vx=10.0;
float vy;

float deltaVx;
float deltaVy;

float mass = 2.0; // Atomic mass unit
float dt = 0.1;

float x_plate_left = 200;
float x_plate_right = 500;

float q = 1; // elementary charge
float E = 5; // basically just Newtons per elementary charge 
              // if you think of pixels as meters
float B = -0.667;

float xinitial;
float yinitial;

//For drawing the image of the particle
PImage img;

//For drawing the direction of the magnetic field
PImage bfld;

void setup() {
  size(775,500);
  smooth();

  xinitial = 0.05*width;
  yinitial = height/2;

  x = xinitial;
  y = yinitial;

  img = loadImage("http://www.physics.ohio-state.edu/~orban/physics1251lab/proton.png");

  if( B < 0 ){
    bfld = loadImage("http://www.physics.ohio-state.edu/~orban/physics1251lab/into_magfield.png");
  } else if (B > 0) {
    bfld = loadImage("http://www.physics.ohio-state.edu/~orban/physics1251lab/oop_magfield.png");
  }

}

// For people with C and C++ experience, draw() is
// very similar to main(), except that draw() 
// is run over and over again 
void draw() {
  
  // Update velocities
  vx += deltaVx;
  vy += deltaVy;

  // Update location
  x += vx*dt;
  y += vy*dt;

  // Set deltaV to zero (thrust off unless user turns it on)
  deltaVx = 0;
  deltaVy = 0;

  if ( ( x > x_plate_left) & (x < x_plate_right))
  {
  deltaVx = (q*E/mass)*dt;
  }

  // If the charge is in the region with the magnetic field  
  if ( x > x_plate_right ) 
  {
  deltaVx = 0.0; // change in vx from magnetic field 
  deltaVy = 0.0; // change in vy from magnetic field
  }

  // Draw ship and other stuff
  display();
  
} // end draw()