polyline weirdness

blah.cpp

#include "testApp.h"

//--------------------------------------------------------------
void testApp::setup(){
    ofSetCircleResolution(6);
    _x = ofGetWidth()/2;
    _y = ofGetHeight()/2;
    _r = ofGetWidth()/5;


    ofSetVerticalSync(true);
    ofBackgroundHex(0xfdefc2);
    ofSetLogLevel(OF_LOG_NOTICE);

    box2d.init();
    box2d.setGravity(10, 0);
    box2d.setFPS(30.0);
    box2d.registerGrabbing();

    int buffer=200;
    p.addVertex(buffer,buffer);
    p.addVertex(ofGetWidth()-buffer,buffer);
    p.addVertex(ofGetWidth()-buffer,ofGetHeight()-buffer);
    p.addVertex(buffer,ofGetHeight()-buffer);
    //p.addVertex(buffer,buffer);
    p.close();

    ofxBox2dCircle c;
    for(ofPoint v : p.getResampledBySpacing(20).getVertices()){
        cout << v.x << ":" << v.y << endl;
        c.setup(box2d.getWorld(),v.x,v.y,20);
        anchors.push_back(c);
    }

    mouse.setup(box2d.getWorld(),ofGetWidth()/2,ofGetHeight()/2,20);

    // now connect each anchor with a joint
    for (int i=0; i<anchors.size(); i++) {

        ofxBox2dJoint joint;

        joint.setup(box2d.getWorld(), anchors[i].body, anchors[(i+1)%4].body);

        joint.setLength(20);
        joints.push_back(joint);
    }
    

}

//--------------------------------------------------------------
void testApp::update(){
    box2d.update();
}

//--------------------------------------------------------------
void testApp::draw(){

    ofSetHexColor(0xf2ab01);
    mouse.draw();
    p.draw();

    for(ofxBox2dCircle b : anchors) {
        ofFill();
        ofSetHexColor(0x01b1f2);
        b.draw();
    }

    for(int i=0; i<joints.size(); i++) {
        ofSetHexColor(0x444342);
        joints[i].draw();
    }

    string info = "";
   // info += "FPS: "+ofToString(ofGetFrameRate(), 1)+"\n";
    ofSetHexColor(0x444342);
    ofDrawBitmapString(info, 30, 30);
}

//--------------------------------------------------------------
void testApp::keyPressed(int key){
    if(key == 't') ofToggleFullscreen();
}

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

}

//--------------------------------------------------------------
void testApp::mouseMoved(int x, int y ){
    mouse.setPosition(x, y);
}

//--------------------------------------------------------------
void testApp::mouseDragged(int x, int y, int button){

}

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

}

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

}

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

}

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

}

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

}

blah.h

#pragma once

#include "ofMain.h"
#include "ofxBox2d.h"

class testApp : public ofBaseApp{

	public:
		void setup();
		void update();
		void draw();

		void keyPressed(int key);
		void keyReleased(int key);
		void mouseMoved(int x, int y );
		void mouseDragged(int x, int y, int button);
		void mousePressed(int x, int y, int button);
		void mouseReleased(int x, int y, int button);
		void windowResized(int w, int h);
		void dragEvent(ofDragInfo dragInfo);
		void gotMessage(ofMessage msg);

        int _x, _y, _r;
        ofxBox2d box2d;
        ofxBox2dCircle mouse;
        vector <ofxBox2dCircle> circles;
        vector <ofxBox2dCircle> anchors;
        vector <ofxBox2dJoint> joints;

        ofPolyline p;
};