Creat a ofCircle every x numbers of pixels

beginners
1

Hello everyone,

I can’t figured out how to create an ofBall every x numbers of pixels in the mouseDragged method. I create a ofBall vector and write:

void ofApp::mouseDragged(int x, int y, int button){
for (int i = 0; i < _ofBall.size(); i++){
    
    ofBall _tempBall;
    _tempBall.draw(100,100,40)
    _ofBall.push_back(_tempBall);
}

 }

So, I want to create x number of balls every 20 pixels for example. What I have to do?.

Thank you so much.

2

You’ll need variables to hold the positions of the mouse the last time the “balls” were added to the vector. Let’s say each 20 pixels, you want to add 5 balls to your vector.

In testApp.h, create the variables to hold the position:

float lastBallAddX;
float lastBallAddY;

In your mouse dragged function, write an if statement using ofDist function to see if the distance from the last time you added a ball, it is at least 20 pixels of distance away. Don’t forget to update your variables to the new position to be tested.

void ofApp::mouseDragged(int x, int y, int button){

if (ofDist (x, y, lastBallAddX, lastBallAddY) > 20) {

	for (int i = 0; i < 5; i++){
	    ofBall _tempBall;
	    _ofBall.push_back(_tempBall);
	}

	lastBallAddX = x;
	lastBallAddY = y;

    }
}
3

Hi @bschorr, thank you so much for your quickly reply. This is not exactly what I want to do. I want to create an infinity number of balls while i’m dragging the mouse along the screen. If I dragged from the left side to the middle I would create n number of balls (for example, 1 ball every 20 pixels). I think I have to use the ofDist function but inside when I create the for what I have to write instead of number 5?.

Thank you so much.

4

Hey @noobie, I’m not quite sure what you want to do… by “create”, you mean “draw to the screen”? Are the balls a separate class? There’s no such thing as an ofBall in OpenFrameworks… Do you mean ofCircle?

By infinity number of balls, you mean to draw them in a random part of the screen?.. Or do you mean under the mouse? Do you expect your balls to animate once they are “created”?.. Please be more specific and I can try to help.

Good luck in these beginnings! It gets better soon :wink:

5

My apologies @bschorr.

Yes, i have a class that draw a ball (ofCircle) but my class is named ofBall like the classes used in the tutorial page. So, what I want to do is create an n numbers of ball every 20 pixels between them along the x axis while you are dragging the mouse along the screen.

For example: If I dragg the mouse along the screen on the x = 300 axis the first ball will appear at 300, the next one at 320, the next one at 340 … all them will have the same y, until I release the mouse.

Thank you so much.

6

Some help?

7

Bump!

8

I’m not entirely sure what you want to achieve…

If you want to create some Balls starting when you press the mouse, along the y-as, with an 20px spacer between them, until you release the mouse you could do something like :

ofApp.h ::

#pragma once

#include "ofMain.h"

class testApp : public ofBaseApp{
public:
    void setup(){
        ofBackground(0);
    }
    void update(){
        if ((ofGetMousePressed())&&(ofGetFrameNum()%dropAmount==0)) {
            circles.push_back(lastMousePressed);
            lastMousePressed.x+=jumpAmount;
        }
    }
    
    
    void draw(){
        ofSetColor(ofColor::white);
        for (auto it(circles.begin()); it != circles.end();) {
            (*it).y += fallDownAmount;
            if ((*it).y >= ofGetHeight()) {
                it = circles.erase(it);
            } else {
                ofCircle((*it), circleRadius);
                it++;
        }   }   }
		
    void mousePressed(int x, int y, int button){
        lastMousePressed = ofPoint(x,y);
    }
    
private:
    ofPoint lastMousePressed;
    vector<ofPoint> circles;
    const int jumpAmount = 20;
    const int dropAmount = 20;
    const int circleRadius = 10;
    const int fallDownAmount = 1;
};

Or if you want the “balls” to drop from your current mouse x (instad of the fixed “jumpAmount”) you could change the update function to:

void update(){
        if ((ofGetMousePressed())&&(ofGetFrameNum()%dropAmount==0)) {
            circles.push_back(ofPoint(ofGetMouseX(), lastMousePressed.y));
        }
    }

hope this helps…