trying to figure out setupOffAxisViewPortal

gistfile1.txt

// make a sphere
    ofSpherePrimitive sph;
    sph.set(100, 10);
    ofMesh s = sph.getMesh();
    
    // grab the current camera
    // this is to figure out where a camera "should" be, ie, for this overall picture where is the camera.
    ofCamera mainCam;
    mainCam.setupPerspective();
    
    // grab the main viewport also
    ofRectangle mainViewport = ofGetCurrentViewport();
    
    // this is the camera that we will be doing the off axis stuff with
    ofCamera subViewCam;
    
    for (int i = 0; i < 3; i++){
        
        // let's look at the scene in 3s
        
        ofRectangle subView = mainViewport;
        subView.width/=3.0;
        subView.x += subView.width * i;
        
        // move to the subview & scissor test
        
        ofViewport(subView);
        glEnable(GL_SCISSOR_TEST);
        glScissor(subView.x, subView.y, subView.width, subView.height);
        ofClear(i*90, 255,255);
        
        
        if (ofGetMousePressed()){
            
            // not sure what's the best way to show this *not* working
            subViewCam.setupPerspective();
            //subViewCam.setPosition(subView.width * i + subView.width/2, subView.height/2, -mainCam.getPosition().z);
        } else {
            subViewCam.setPosition(mainViewport.width/2, mainViewport.height/2, -mainCam.getPosition().z);  // camera is based on where it would be normally for a window this size.
            subViewCam.lookAt( ofPoint(subView.getWidth()/2, subView.getHeight()/2));
            subViewCam.setupOffAxisViewPortal(subView.getTopLeft(), subView.getBottomLeft(), subView.getBottomRight());
            subViewCam.setScale(1, 1, 1);
            subViewCam.setNearClip(0.1);
        }
        
        
        
        subViewCam.begin();
        ofFill();
        ofPushMatrix();
        if (ofGetMousePressed()){
            ofTranslate(mouseX - subView.width * i, mouseY);
        } else {
            ofTranslate(mouseX, mouseY);
        }
        
        
        //ofRect(0,0,50,50);
        ofSetColor(ofColor::darkBlue);
        sph.drawWireframe();
        ofPopMatrix();
        subViewCam.end();
        
        // draw a bounding box around each scene
        
        glDisable(GL_SCISSOR_TEST);
        ofViewport(mainViewport);
        ofSetColor(255);
        ofSetLineWidth(5);
        ofNoFill();
        ofRect(i*subView.width,0, subView.width, subView.height);
        ofSetLineWidth(1);
        
    }
    
    ofDrawBitmapStringHighlight("mouse pressed = non offaxis cam..", ofPoint(50,50));