Projectile Game: The ball doesn't sit on the ground, only half shows up

arwa1203

Hi, I'm doing a project that's due soon for intro to engineering and comp sci class in which I have to shoot a ball out of a cannon. Everything seems to be working fine except that when the ball hits the ground, only half of it shows up. I think it's because I stop the ball from moving when ypos=0 which is the center of the ball. I want all of the ball to be resting on the ground. I was wondering if anybody knew how to fix this issue.

float v;           // velocity
float g;           // gravity constant 32 ft
float t_time;      // total time
float cur_time;    // current time
float cannonAngle; // angle the ball will be shot
float firingAngle; // angle of the ball

float xpos;        // function for the x position of the ball
float ypos;        // function for the y position of the ball

int targetStart;
int targetWidth = 25;
int attempt;       // the number of times the ball has been shot
String status;

void setup ()
{
  size(800,300);      // size of the screen
  v=150;              // velocity
  cannonAngle=radians(45);           // angle of cannon
  firingAngle=cannonAngle;
  g=32;
  t_time =0;
  cur_time=0;
  targetStart = int(random(100, width-targetWidth));
  attempt = 0;
  status = "Halt";
  xpos=0;
  ypos=0;
}


void draw ()
{
  PImage img = loadImage("mountains.png");  // background image
  image(img, 0, 0);

 if (status == "Run"){
    if (cur_time>t_time){  
      checkTarget(); // Stop animation
    }
    else if(cur_time<t_time){
      cur_time += 0.080;    // add 0.050 to the current time
    }

  } 


 fill(0);                 // black color

 drawTarget();
 drawShot();    // shows the ball moving across the screen

 PImage wheelback=loadImage("wheel_b.png");        // stationary back wheels
 image(wheelback, 5, 271);
 drawCannon();
 PImage wheelfront=loadImage("wheel_f.png");      // stationary front wheel
 image(wheelfront, -5, 268);

 drawPosition ();                                // text in the corners

 //reset();                                     // makes ball sit on ground
}



/* Functions */


void reset()                                   // resetting the ball back ot the beginning
{
  if (cur_time>t_time)                         // if y pos ever goes off the screen
  {
    ypos=height-27;            

  }
}


// draws the ball the screen
void drawShot ()
{
 xpos= v*cur_time*cos(firingAngle);                            // x position
 ypos = v*cur_time*sin(firingAngle)-(0.5*(g*(sq(cur_time))));  // y position
 fill(116,46,0);
 ellipse(xpos, height-ypos, 10, 10);                     
 if(ypos<0)                                                    // if the y position is greater than ground,
 {
   ypos=0 ;                                                    // set ypos equal to zero
 }
}  

// draws the cannon
void drawCannon() {
  // Start new shape translations
  pushMatrix(); 
  fill(0);
  // Move screen origin to the lower left hand corner
  translate(0, height-10); 
  // Rotate new shapes cannonAngle degrees counter-clockwise
  rotate(cannonAngle * -1); 
  // Draw rectangle with the new origin and rotation
  fill(80,32,0);
  rect(0, 0, 50, 15);
  // reset shape translations
  popMatrix();  
}

// fires the shot
void fireCannon() 
{
  cur_time = 0;
  firingAngle = cannonAngle;
  t_time = (2*v*sin(firingAngle)/g);
  attempt++;
  status = "Run";
}

// when user presses key
void keyPressed() 
{
  if(key == CODED && keyCode == LEFT)
  {
    cannonAngle = cannonAngle + .01;
    if(cannonAngle > HALF_PI){
      cannonAngle = HALF_PI;
    }
  }
  else if(key == CODED && keyCode == RIGHT) {
    cannonAngle = cannonAngle - .01;
    if(cannonAngle<=0.0)
    {
      cannonAngle=0.0;
    } 
  }
  else if(key == ' ') {
    cur_time = 0.0;
    firingAngle = cannonAngle;
    fireCannon();
  }
}

// draws the target

void checkTarget() {

  if (xpos >= targetStart && xpos <= targetStart + targetWidth) {

    status = "HIT";
  }
  else {

   status = "MISS";
  }
}
void drawTarget() {
  strokeWeight(5);
  stroke(255, 0, 0);
  line(targetStart, height-1, targetStart + targetWidth, height-1);
  stroke(0);
  strokeWeight(0);
}


// writes the texts in the corners and such
void drawPosition()
{
      fill(255);
      rect(2,2, 160, 80);
      fill(0);
      String text = "Time (sec): " + nf(cur_time, 1, 2)
                  + "\nCoordinates: (" + int(xpos) + " , " + int(ypos)+")"
                  + "\nCannon Angle: " + degrees(cannonAngle)
                  + "\nAttempt(s): " + attempt
                  + "\nStatus: " + status;
      text(text, 10, 20);


}

billautomata

The diameter of your ellipse is 10. Just make the ground yPos=5 (half of the ellipse) ?

 if(ypos<5)                                                    // if the y position is greater than ground,
 {
   ypos=5;                                                    // set ypos equal to zero
 }

arwa1203

It doesn't really make a difference except that at different angles the ball would sometimes be totally off the screen or still halfway, as shown in the pictures.

Actually it does that even if ypos=0.