Simple 3D Spring

#include "testApp.h"

ofEasyCam camera;
ofVec3f posA, posB;
ofVec3f velA, velB;

bool bTouchingA, bTouchingB;
bool bPressedA, bPressedB;

static float minMouseDis = 15.0;

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

    ofEnableDepthTest();
    bTouchingA = bTouchingB = false;
    bPressedA  = bPressedB  = false;
    
    camera.setDistance(50);
    
    posA.set(0, 0, 0);
    posB.set(20, 0, 0);
}

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

    float restLength  = 15.0;
    float springiness = 0.03;
    
    ofVec3f vec     = posB - posA;
    float   dis     = vec.length();
    float   k       = -1;
    float   spring  = (springiness * (restLength - dis)) * k;
    
    vec.normalize();
    ofVec3f frc = vec * spring;
    
    if(!bPressedA) {
        velA += frc;
        velA *= 0.96;
        posA += velA;
    }

    if(!bPressedB) {
        velB -= frc;
        velB *= 0.96;
        posB += velB;
    }
}

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

    camera.begin();
    
    ofNoFill();
    ofSetColor(90);
    ofDrawBox(0, 0, 0, 100, 100, 100);
    ofFill();
    
    (bTouchingA || bPressedA) ? ofSetColor(0, 255, 0) : ofSetColor(255, 0, 0);
    ofDrawSphere(posA, 1);
    
    (bTouchingB || bPressedB) ? ofSetColor(0, 255, 0) : ofSetColor(255, 255, 0);
    ofDrawSphere(posB, 1);
    
    ofSetColor(255);
    ofLine(posA, posB);
    
    
    
    camera.end();
}

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

}

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

}

//--------------------------------------------------------------
void testApp::mouseMoved(int x, int y ) {
    
    ofVec2f mouse(ofGetMouseX(), ofGetMouseY());
    bTouchingA = ofVec2f(camera.worldToScreen(posA)).distance(mouse) < minMouseDis;
    bTouchingB = ofVec2f(camera.worldToScreen(posB)).distance(mouse) < minMouseDis;
}

//--------------------------------------------------------------
void testApp::mouseDragged(int x, int y, int button){
    
    ofVec3f cameraMouse = camera.screenToWorld(ofVec2f(ofGetMouseX(), ofGetMouseY()));

    if(bPressedA) {
        posA.set(cameraMouse);
    }
    
    if(bPressedB) {
        posB.set(cameraMouse);
    }
}

//--------------------------------------------------------------
void testApp::mousePressed(int x, int y, int button){
    
    ofVec2f mouse(ofGetMouseX(), ofGetMouseY());
    bPressedA = ofVec2f(camera.worldToScreen(posA)).distance(mouse) < minMouseDis;
    bPressedB = ofVec2f(camera.worldToScreen(posB)).distance(mouse) < minMouseDis;
    
    if(bPressedA || bPressedB) {
        camera.disableMouseInput();
    }
}

//--------------------------------------------------------------
void testApp::mouseReleased(int x, int y, int button){
    
    camera.enableMouseInput();
    bPressedA = bPressedB = false;
}

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

}

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

}

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

}