title: Potree Zoom in/out on click
body: <p>I am trying to zoom in/out when the user clicks the “+” or “-” buttons on my control panel. I got it to move left, right, up, down with the “tweenFunction” and it worked. I’ve tried</p>
  
  <pre><code>viewer.scene.camera.zoom += 0.1;
  </code></pre>
  
  <p>Which didn’t work for me because I don’t have the “camera” variable in my code, only the viewer. Here is my code</p>
  
  <pre><code>    setup();
      window.viewer = new Potree.Viewer(document.getElementById("potree_render_area"));
  
      viewer.setEDLEnabled(false);
      viewer.setFOV(60);
      viewer.setPointBudget(5*1000*1000);
      document.title = "";
  
      viewer.setBackground("gradient"); // ["skybox", "gradient", "black", "white"];
      viewer.loadSettingsFromURL();
  
      viewer.loadGUI(() =&gt; {
          viewer.setLanguage('en');
          $("#menu_scene").next().show();
          //viewer.toggleSidebar();
      });
  
      viewer.setDescription(`
  
      `);
  
      let sceneSG = new Potree.Scene();
      let sceneSG2 = new Potree.Scene();
  
      viewer.setScene(sceneSG);
  
    Potree.loadPointCloud("model.js", "model", function (e){
  
          sceneSG.addPointCloud(e.pointcloud);
          sceneSG.view.position.set(37.812, -26.781, 51.178);
          sceneSG.view.lookAt(new THREE.Vector3(-53.587, 33.834, 28.864));
  
  
          let material = e.pointcloud.material;
          material.size = 1;
          material.pointSizeType = Potree.PointSizeType.ADAPTIVE;
  
      });
  </code></pre>