VP1Doc: Basic navigation and usage of the 3D viewer

It is recommended that any VP1 user quickly familiarise themselves with how to navigate the 3D viewer and pick (i.e. select) 3D objects. This page summarises how to do this, and at the bottom of the page is a movie illustrating all this. You might want to watch the movie both before and after reading all this, and it will be particularly helpful to have an instance of VP1 running so you can try out the controls while reading about them.

Perspective versus Orthographic View Mode

VP1 renders scenes in either perspective or orthographic modes. In the former mode, parallel lines are drawn closer the further they are from the viewer, while this distance is constant in the latter mode. The difference is illustrated with the following images:

The perspective mode provides more realistic and intuitive (and cooler) 3D scenes, and is thus the default. However, in several cases, such as when e.g. viewing a muon chamber head-on, or the inner detector from the Z axis (i.e. an r-phi view), the orthographic mode is more useful.

The 5th button on the right of the viewer is used to toggle between the two modes, and its appearance indicates the current mode: when in perspective mode, and when in orthographic mode. Pressing "C" likewise toggles the two modes, while "P" and "O" goes to perspective and orthographic mode respectively.

Interaction modes

At any given time, the viewer will be in one of two interaction modes: The first is the navigation mode, in which the user can use the mouse to rotate, pan, zoom, etc. The second mode is the pick mode, in which the user can click on 3D objects in the scene, to trigger plugin-specific actions related to that object (such as printing of related information, automatic zooming to that object, etc.).

Navigation and pick modes are entered by pressing the and buttons, respectively. Pressing either ESC or M toggles between the two modes.

Changing the view directly with the mouse

While in navigation mode, here is how to change the view with the mouse (if you have a laptop, an external USB mouse is strongly recommended):

• Rotating: Click and hold down the left mouse button. Note that there is a centre for this rotation which might be far away from the 3D objects you are interested in, making this manoeuvre quite difficult. You can choose a new centre for the camera after either clicking the button or pressing "S" (the viewer will initially zoom a bit towards the new centre).
• Zooming: The easiest is probably to use a mouse-wheel. Alternatively, clicking left and middle mouse button at the same time will allow you to zoom by moving the mouse up and down.
• Panning: Click and hold the middle mouse button. Alternatively, hold down shift or control and use the left mousebutton (this is useful for e.g. Mac users).

It is also possible to leave the scene spinning all by itself. spinning

Changing the view using other controls

• Buttons which zooms to one of four regions: Vertex, Inner detector, Calorimeters, or the Muon system. The view will end up looking from either the positive or negative Z axis, respectively. In orthographic view mode, the resulting view will just be an r-phi projection of the detector. These buttons are particularly useful when doing Inner Detector or vertex studies, as they immediately brings the relevant parts into the view, saving the user a lot of manual zooming.
• Rotate the view along an axis coming straight out of the screen. This is mainly useful when you have just used the previously described buttons to bring view up an r-phi projection, which you can then rotate (i.e. change what is "up"
• Rotate the view along an axis which is "vertical" on the screen. This corresponds to left-clicking and dragging the mouse exactly from left to right.
• Simply zooms in and out.
• (shortcut "S"): This button, which we already introduced above, will put the viewer into seek mode (the cursor becomes a cross-hair). Subsequently selecting a point on any 3D object will set a new center for the view, and will zoom towards the point.
• (shortcut "V"): Zooms out (or in) far enough for all objects to become visible.

Context menu (basic)

When in navigation mode, right-clicking anywhere in the viewer brings up a context menu:

For now we will just introduce the most useful entries, all visible in the snapshot above:

• Background Colour: Not surprisingly, this brings up a dialog allowing one to change the background colour.
• Anti aliasing (shortcut "A"): Toggles whether or not to employ anti aliasing. In most cases, anti aliasing gives a better visual result, but might also slow down the rendering performance somewhat.
• Reset camera: Brings back the view to its initial setting. This is sometimes useful, since it is possible for the view-parameters (in particular parameters related to perspective and the so-called clipping-planes) to get somewhat messed up occasionally. Choosing this option gets out of that particular mess.

The rest

The button, and the rest of the context menu, will be discussed on a different page (todo).

Movie showcasing all this