Simple testApp.cpp for a moving ball in openFrameworks.

testApp.cpp

//BALL "TUTORIAL" FOR SUSANA RIBEIRO

#include "testApp.h"

//FIRST WE NEED TO DECLARE SOME THINGS ABOUT A "BALL"

struct BallStructure {
    ofPoint position;   //A BALL HAS A POSITION
    int radius;         //AND A RADIUS OF COURSE    
    ofColor color;      //AND WE LIKE TO LET IT HAVE A COLOR
    ofPoint direction;  //A BALL HAS SPEED IN SOME DIRECTION
};

//OK, NOW WE KNOW HOW A BALL LOOKS LIKE; SO WE CAN CREATE ONE:

BallStructure myFirstBall;

//--------------------------------------------------
void testApp::setup() {
    //HERE WE ARE SETTING THE RATE AT WHICH WE THE PROGRAM WILL RUN (AND HOW MANY TIMES PER SECOND THE UPDATE AND DRAW METHODS ARE CALLED IT IN FRAMES PER SECOND)
    ofSetFrameRate(60);
    
    //NOW WE TELL THE FIRST BALL HOW IT LOOKS LIKE:
    
    //FIRST WE GIVE IT A RANDOM POSITION
    myFirstBall.position.x = ofRandom(0,ofGetWidth());
    myFirstBall.position.y = ofRandom(0,ofGetHeight());
    
    //AND A RADIUS
    myFirstBall.radius = ofRandom(10,30);
    
    //AND THE COLOR
    myFirstBall.color = ofColor::fromHsb(ofRandom(0,255),255,255);
    
    //AND A RANDOM SPEED/DIRECTION
    myFirstBall.direction.x = ofRandom(-15,15);
    myFirstBall.direction.y = ofRandom(-15,15);
    
}

//--------------------------------------------------
void testApp::update() {
    //HERE WE UPDATE THE POSITION OF THE BALL BASED ON THE SPEED/DIRECTION
    myFirstBall.position = myFirstBall.position + myFirstBall.direction;
    
    //HERE WE CHECK IF WE REACHED THE BORDERS OF THE WINDOW AND BOUNCE IT BACK
    if (myFirstBall.position.x < 0) {
        myFirstBall.direction.x = abs(myFirstBall.direction.x);
    }
    if (myFirstBall.position.y < 0) {
        myFirstBall.direction.y = abs(myFirstBall.direction.y);
    }
    
    if (myFirstBall.position.x > ofGetWidth()) {
        myFirstBall.direction.x = -abs(myFirstBall.direction.x);
    }
    
    if (myFirstBall.position.y > ofGetHeight()) {
        myFirstBall.direction.y = -abs(myFirstBall.direction.y);
    }
    
}



//--------------------------------------------------
void testApp::draw() {
    //NOW WE CAN DRAW THE BALL
    
    //FIRST WE SET THE COLOR
    ofSetColor(myFirstBall.color);
    
    //AND NOW WE CAN DRAW A CIRCLE AT THE POSITION OF THE BALL WITH ITS RADIUS
    ofCircle(myFirstBall.position,myFirstBall.radius);
}