mid-point code for Week 6

ofApp.cpp

#include "ofApp.h"

#define NUM_PARTICLES 100

float radius = 5;
vector<ofPoint> pos;
vector<ofPoint> vel;
vector<float> alpha;

ofPoint lastMousePos;

//--------------------------------------------------------------
void ofApp::setup(){

}

//--------------------------------------------------------------
void ofApp::update(){
    
    for(int i=pos.size()-1; i>=0; i--) {
        pos[i] += vel[i];
        alpha[i] *= 0.99;
        
        if(pos[i].x > ofGetWidth()-radius) {
            pos[i].x = ofGetWidth()-radius;
            vel[i].x *= -1;
        }
        if(pos[i].y > ofGetHeight()-radius) {
            pos[i].y = ofGetHeight()-radius;
            vel[i].y *= -1;
        }
        if(pos[i].x < radius) {
            pos[i].x = radius;
            vel[i].x *= -1;
        }
        if(pos[i].y < radius) {
            pos[i].y = radius;
            vel[i].y *= -1;
        }
        
        if(alpha[i] < 1) {
            pos.erase(pos.begin()+i);
            vel.erase(vel.begin()+i);
            alpha.erase(alpha.begin()+i);
        }
    }
}

//--------------------------------------------------------------
void ofApp::draw(){
    
    for(int i=0; i<pos.size(); i++) {
        ofSetColor(0, alpha[i]);
        ofDrawCircle(pos[i], radius);
    }
    
    ofSetColor(0);
    ofDrawBitmapString(ofToString(pos.size()) + "\n" + ofToString(ofGetFrameRate()), 10, 20);
}

//--------------------------------------------------------------
void ofApp::keyPressed(int key){

}

//--------------------------------------------------------------
void ofApp::keyReleased(int key){

}

//--------------------------------------------------------------
void ofApp::mouseMoved(int x, int y ){
    
}

//--------------------------------------------------------------
void ofApp::mouseDragged(int x, int y, int button){
    
    
    ofPoint p(x,y);
    pos.push_back( p );
    
    ofPoint v = p-lastMousePos;
    v.limit(5);
    v.x += ofRandom(-4, 4);
    v.y += ofRandom(-4, 4);
    vel.push_back( v );
    
    alpha.push_back(255);

    lastMousePos.set(x,y);
}

//--------------------------------------------------------------
void ofApp::mousePressed(int x, int y, int button){

}

//--------------------------------------------------------------
void ofApp::mouseReleased(int x, int y, int button){

}

//--------------------------------------------------------------
void ofApp::mouseEntered(int x, int y){

}

//--------------------------------------------------------------
void ofApp::mouseExited(int x, int y){

}

//--------------------------------------------------------------
void ofApp::windowResized(int w, int h){

}

//--------------------------------------------------------------
void ofApp::gotMessage(ofMessage msg){

}

//--------------------------------------------------------------
void ofApp::dragEvent(ofDragInfo dragInfo){ 

}