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# Simple physics

edited April 2015

This is a simple code to play with physics.

``````//time
int lastMillis = 0;

//character
float positionX = 1;
float positionY = 1;
float sizeX = 0.1;
float sizeY = 0.1;
float velocityX = 0.0;
float velocityY = 0.0;
float gravity = 0.1;
boolean onGround = false;
float jumpSpeed = 0.06;
float moveSpeed = 0.002;

//world
float floorFriction = 0.1;
float airFriction = 0.1;
float depreciser = 0.0005;
int worldHeight = 2;
int worldWidth = 2;
int worldScale = 500;
float bounciness = 0.7;

int deltaTime() //time in milliseconds between each frames
{
int delta = millis() - lastMillis;
lastMillis = millis();
return delta;
}

//you can override this
boolean canJump() { return onGround;}

void inputs()
{
//jump
if (mousePressed && canJump())
{
velocityY -= jumpSpeed;
}
if (keyPressed)
{
//move left
if(key == 'a'|| key == 'A' || key == 'q'|| key == 'Q' ) {
velocityX -= moveSpeed;
}
//move right
if(key == 'd' || key == 'D') {
velocityX += moveSpeed;
}
//jump
if(key == ' ' && canJump()) {
velocityY -= jumpSpeed;
}
}
}

void setup()
{
size(worldWidth * worldScale, worldHeight * worldScale);
}

void draw()
{
float deltaTime =  ((float)deltaTime())/1000.0;

//gravity
velocityY += gravity*deltaTime;

//inputs
inputs();

//airFriction
velocityX -= airFriction*moveSpeed * velocityX;
velocityY -= airFriction*moveSpeed * velocityY;

//floor friction
if (onGround)
{
velocityX -= floorFriction * velocityX;
}

if (abs(velocityX) <= depreciser) velocityX = 0;

//set new position
positionX += velocityX;
positionY += velocityY;

//hits
//hit ground
if (positionY + sizeY/2 >= worldHeight)
{
positionY = worldHeight - sizeY/2;
velocityY = -velocityY*bounciness;
onGround = true;
} else
{
onGround = false;
}
//hit walls
if (positionX + sizeY/2 >= worldWidth || positionX - sizeY/2 <= 0)
{
if (positionX + sizeY/2 >= 2)
{
positionX = worldWidth - sizeY/2;
}

if (positionX - sizeY/2 <= 0)
{
positionX = 0 + sizeY/2;
}
velocityX = -velocityX*bounciness;
}

//draw
background(0);
noStroke();

fill(102);
rect((positionX - sizeX/2) * worldScale, (positionY - sizeY/2) * worldScale, sizeX * worldScale, sizeY * worldScale);

}
``````
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