Animate bouncing box using? - c++

Question

I need to make an animation where the box starts from (-15, 0) then going up to (-8, 15) and when it reach that, then it came down. and so on, just like a DVD screen saver, but i can't seem to find the formula for it to work.
Here's the code:
#include<windows.h>
#include<GL/glu.h>
#include<GL/glut.h>
#ifdef APPLE
#include<GLUT/glut.h>
#else
#include<GL/glut.h>
#endif
#include<stdio.h>
#include<stdlib.h>
#include <GL/freeglut.h>
//Variable menampung sudut awal
float xpos = -15.0;
float deltax = 0.5;
float ypos = 0.0;
bool balik = true;
bool turun = true;
//Variable mengatur perubahan sudut
void myInit(void) {
glClearColor(0.0, 0.0, 0.0, 1.0);
glColor3f(1.0, 1.0, 1.0);
glPointSize(2.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-15.0f, 15.0f, -15.0f, 15.0f);
}
void myDisplay(void) {
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_LINES);
glColor3f(1.0, 1.0, 1.0);
glVertex2f(-15.0, 0.0);
glVertex2f(15.0, 0.0);
glEnd();
glBegin(GL_LINES);
glColor3f(1.0, 1.0, 1.0);
glVertex2f(-8.0, 15.0);
glVertex2f(-8.0, -15.0);
glEnd();
glBegin(GL_LINES);
glColor3f(1.0, 1.0, 1.0);
glVertex2f(8.0, 15.0);
glVertex2f(8.0, -15.0);
glEnd();
glBegin(GL_LINES);
glColor3f(1.0, 1.0, 1.0);
glVertex2f(0.0, 15.0);
glVertex2f(0.0, -15.0);
glEnd();
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_POLYGON);
glVertex2f(-0.2 + xpos, 0.2 + ypos);
glVertex2f(-0.2 + xpos, -0.2 + ypos);
glVertex2f(0.2 + xpos, -0.2 + ypos);
glVertex2f(0.2 + xpos, 0.2 + ypos);
glEnd();
glutSwapBuffers();
}
void Timer(int) {
glutPostRedisplay();
glutTimerFunc(100, Timer, 0);
if (ypos < 15 && xpos <-8 && turun == true){
xpos = xpos + deltax;
ypos = (2.143*xpos) + 32.143;
}
else {turun = false;};
if (ypos > -15 && xpos <8 && turun == false){
xpos = xpos + deltax;
ypos = -1,875*xpos + ;
}
else turun = true;
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCreateWindow("Animasi");
glutDisplayFunc(myDisplay);
myInit();
glutTimerFunc(0, Timer, 0);
//Perulangan
glutMainLoop();
return 0;
}

Answer 1

If you want the box to bounce you can just reverse the x or y velocity depending on which axis you hit. If you want the box to bounce with Gravity you will use vector parametric equations like so:
y = -16t^2 + vsin(x) + s.y and x = vcos(x) + s.x where t is time v is magnitude(velocity) and s is the starting position of the box which will be reset on every collision with the sides. Keep the magnitude the same to infinitely bounce. If the equation is confusing look up vector pre-calculus online.