gravity.c

#include <simple2d.h>
#include <stdio.h>
#include <time.h>
#include <math.h>

//constants to use for ball direction and boolean
#define LEFT -1
#define RIGHT 1
#define UP -1
#define DOWN 1
#define FALSE 0
#define TRUE 1

#define torad(angleInDegrees) ((angleInDegrees) * M_PI / 180.0)

float previousTime = 0;
float currentTime;
float dt;

typedef struct {
  float x;
  float y;
}vector;

typedef struct {
  int r;
  vector p;
  vector v;
  vector g;
  int dir_x;
  int dir_y;
}ball;

ball _ball;

const int screen_width = 640;
const int screen_height = 480;

vector Vector(float x, float y){
  vector _Vector;
  _Vector.x = x;
  _Vector.y = y;
  return _Vector;
}

vector addV(vector va, vector vb){
    vector returnVector;
    returnVector.x = va.x + vb.x;
    returnVector.y = va.y + vb.y;
    return returnVector;
}

vector subV(vector va, vector vb){
    vector returnVector;
    returnVector.x = va.x - vb.x;
    returnVector.y = va.y - vb.y;
    return returnVector;
}

vector multiplyV(vector va, float coef){
    vector returnVector;
    returnVector.x = va.x * coef;
    returnVector.y = va.y * coef;
    return returnVector;
}

void update() {

    if(_ball.p.x >= (screen_width-_ball.r)){ //hit right side
        _ball.dir_x = LEFT; //bounce back by going left
    }    else if(_ball.p.x <= _ball.r) { //hit left side
            _ball.dir_x = RIGHT; //bounce back right
            }

    //_ball.p.x += _ball.v.x * _ball.dir_x; //position _ball x pos

    if(_ball.p.y >= (screen_height-_ball.r)){ //hit bottom
        _ball.dir_y = UP; //bounce up
    }    else if(_ball.p.y <= _ball.r){ //hit top
            _ball.dir_y = DOWN; //bounce down
            }

    //_ball.p.y += _ball.v.y * _ball.dir_y; //position _ball y pos



  _ball.p = addV(_ball.p, multiplyV(_ball.v, dt));
  _ball.v = addV(_ball.v, multiplyV(_ball.g, dt));

}

void render() {
    S2D_DrawCircle(_ball.p.x, _ball.p.y, _ball.r, 50, 1, 0, 0, 1);

}


int main() {
    dt = 1.0 / 20.0;
    int angle;
    _ball.g = Vector(0, 5);
    _ball.v = Vector(20, -50);
    _ball.r = 30;
    _ball.p = Vector(100,480-30);
    /*angle = (rand() % 90)+1;
    if(angle >= 0 && angle <= 45){
      _ball.v.y = 5;
      _ball.v.x = tan(torad(angle)) * _ball.v.y;
    } else {
      _ball.v.x = 5;
      _ball.v.y = (1 - tan(torad(angle-45))) * _ball.v.x;
    }*/
    _ball.dir_x = RIGHT;
    _ball.dir_y = DOWN;


    S2D_Window *window = S2D_CreateWindow(
        "Hello Triangle", screen_width, screen_height, update, render, 0);//init the window

    S2D_Show(window);//show the window

    return 0;
}