Hi, I've tried to make a sketch of a bouncin ball with gravity. Muy problem is that my ball bonce higher and higher. I have a hint of the cause, but Im not finishing finding the solution:

Because I increase y coordinate in an undeterminate amount each time, when the ball pass the floor, I have to correct this coordinate to height size, and there is an error there.

Because is complicated to correct it exactly, I´ve tried to correct it making the ball bounce lower and lower, so I subtract the gravity when it bounce in the floor. Well I add because y coordinates increases downside.

This is the code:

Code:

float x=100;
float yin=100;
float y;
float exceso;
float vx=10;
float gravedad=0.8;
float vy=0;
float diametro= 10;
//principio

void setup(){
  y=yin;
  size(600,600);//tamaño
  background(100);//fondo
  stroke (255);//lápiz
  fill(255);
  smooth(); //dibuja con suavidad
  frameRate(20);//velocidad
}
//dibujo
void draw(){
  background(100); //borra
  ellipse(x,y,diametro,diametro);//dibuja la bola
  x=x+vx;//aumenta x
  y=y+vy;
  vy=vy+gravedad;  
  //rebote
  
  if(y>height-diametro/2){
    vy=-vy+gravedad;
    y=height-diametro/2;
  }  
  if(y<diametro/2){
    vy=-vy;
    y=diametro/2;
  }  
    if(x>width-diametro/2){
    vx=-vx;
    x=width-diametro/2;
  }
  if(x<diametro/2){
    vx=-vx;
    x=diametro/2;
    
  }
} 

Thank you, I've made the changes and it works, I´ve been letting the ball bounce for a long time and it hasn't change its maximun height. But I dont understand wthe reason why my code doesn´t work and yours does.

Now I,ve tried to use the same code to make a simple videogame and the ball bounce lower and lower. I can´t see any difference between both codes. In fact I used copy and paste.

This is the code simplified of the videogame:

Code:

Bola pelota;
Bola jug1;
Bola jug2;
float vel=2;
float dista;
float gravedad=1.5;
boolean der1;
boolean izq1;
boolean der2;
boolean izq2;
//principio

void setup(){
  size(500,350);//tamaño
  pelota=new Bola(0,10,10,0,20);
  jug1=new Bola(width/4,height-100,0,4,70);
  jug2=new Bola(width*3/4,height-100,0,4,70);
  background(100);//fondo
  stroke (255);//lápiz
  fill(255);
  smooth(); //dibuja con suavidad
  frameRate(17);//velocidad
}

//dibujo
void draw(){
  background(100); //borra
  rect(width/2,height-200,10,200);
  pelota.bota();
  jug1.bota();
  jug2.bota();
    
  jug1.golpea();
  jug2.golpea();
  mueve();
}


class Bola{
  float x;
  float y;
  float vx;
  float vy;
  float diametro;

  Bola(float xin,float yin,float vxin,float vyin, float diame){
    x=xin;
    y=yin;
    vx=vxin;
    vy=vyin;
    diametro=diame;
  }  
  void bota(){

    ellipse(x,y,diametro,diametro);
    vy=vy+gravedad;
    x=x+vx;//aumenta x
    y=y+vy;
	
    //rebote
    
    if((abs(x-width/2)<diametro/2+5)&&(y>height-200)){
	if(x<width/2){
	  x=width/2-(diametro/2+5);
	}
	else
	{
	  x=width/2+(diametro/2+5);
	}
	vx=-vx;
    }  
    if(y>height-diametro/2){
	vy=-vy;
	y=height-diametro/2;
	
    }  
    if(y<diametro/2){
	vy=-vy;
	y=diametro/2;
    }  
	if(x>width-diametro/2){
	vx=-vx;
	x=width-diametro/2;
    }
    if(x<diametro/2){
	vx=-vx;
	x=diametro/2;
	
    }
  }
  void golpea(){
    dista=sqrt((x-pelota.x)*(x-pelota.x)+(y-pelota.y)*(y-pelota.y));
    if (dista<diametro/2+pelota.diametro/2){
	do{
	    dista=sqrt((x-pelota.x)*(x-pelota.x)+(y-pelota.y)*(y-pelota.y));
	    pelota.y-=pelota.vy/sqrt(pelota.vy*pelota.vy);
	}
	while (dista<=diametro/2+pelota.diametro/2);
	pelota.vy*=-1;
	if(pelota.x<x){	 
	  pelota.vx=-abs(pelota.vx);
	}
	else{
	  pelota.vx=abs(pelota.vx);
	}
    }
  } 
}

void mueve(){
 
    jug1.x+=jug1.vx;
  
    jug2.x+=jug2.vx;
  
  
}