Direct Actions

Direct actions will result in an immediate change.

Reset

Reset is a direct action. It will put the view back into its original state of the projection.

Fit to Window

Fit to Window is a direct action. It will measure the bounding box of the event/geometry in its currently visible state and will Scale and Translate to fit it within the boundaries of the window. The Scaling is uniform. The Translation will center the result.

Interactivity Modes

Of the modes described below only one can be active at a time. The active mode is shown by the corresponding button being depressed, the corresponding menu item in the popup menu being flagged, the corresponding control panel being shown. Any mouse interaction started may be interrupted by pressing the Esc key.

Scaling

Scaling will allow you to enlarge or shrink the picture you are currently seeing. You can also zoom into a region on the screen. When you select the Scaling mode, the control panel will show you a choice of three sub-modes in its Selection box:

• The direct scaling mode scales along the center of the screen. When you drag the left-mouse button in the view towards the center the image will shrink, while when you drag it outwards it will enlarge. Feedback is shown in the form of a circle around the center. This is also the mode which is continuously connected to the mousewheel and works even if another interaction mode is active.
  
  If you click the mousebutton the view will be scaled up by some standard amount. If you alt-click the mousebutton the scaled down by some standard amount.
• The rectangle scaling mode allows you to zoom into a rectangle. When you drag the left-mouse button a fixed ratio rectangle will appear. When released this rectangle will be centered (Translated) and enlarged to fill the view. The view will not be distorted. If, while dragging, you press the shift key, you can select an arbitrary sized rectangle. When released this will be centered and fill the view, however, now the result will be scaled non-uniformly to fill the view.
  
  If you click the mousebutton, the position of the click will be centered and scaled up by some standard amount. Alt-click will produce the opposite result.
• The rotated rectangle scaling mode allows you to zoom into a rotated rectangle. This mode is useful for zooming into tracks at arbitrary angles. When you drag the left-mouse button you will see a line appearing. Drag the line along the track. Now release. You will see a straight or skewed rectangle, along the line just drawn. The ration is fixed, however you have the choice between a straight rectangle, a X-skewed or a Y-skewed rectangle. Click to select one of the three. The picture will now center, rotate, de-skew (if necessary) and scale to fit the view. Deformation of the picture will happen, if you de-skew.
  
  While selecting the final rectangle you may either press the shift key to remove the ratio constraint (the result will deform while scaling) or the ctrl key to remove both ratio constraint and angle (the result will most likely deform, but you can select an arbitrary parallelogram.
  
  If you click (before dragging) allows you to define the rotated rectangle by selecting three points (start center line - end center line - corner point).

Translation

Translation allows you to move the picture anywhere inside the view. Translation (apart from incurred by any of the scaling modes) will only work in direct mode. The control panel will give you no other choice.

When you drag the left-mouse button the picture underneath will follow until you release the mouse button. If you click, the clicked point will be centered. If you alt-click the center will move to the clicked point.

Translations like these will only have an affect on the currently viewed angle. So, if you click on a calorimeter cluster, the cluster will move to the center of the screen, however if you go on to rotate the cluster, you will find that the model is not centered along the screen's Z-axis. In fact what will most likely happen is that the model will float out of the viewable area while you rotate. To select a proper rotation point a 3D translation mode will be added in the near future.

Rotation

The rotation modes are both immediate. From the Selection box you may choose between:

• Rotate in the screen's Z-plane. When you drag the left-mouse button the picture will rotate over the center of the view. Clicking has no function.
• Rotate in 3D using a virtual ball. When you drag the left-mouse button the picture will rotate as if captured by a ball which you roll to any side. Although it is possible by small circular movements to rotate the picture in the screen's Z-plane, the option above is easier. By holding down the shift key while dragging rotation will be limited to the screen's Y-axis, while the ctrl key will limit rotation to the screen's X-axis. Clicking has no function.

Picking

Picking allows the user to show information attached to the objects shown in the view. This attributes can be physics values or other relevant information. When you select the picking mode the control panel will allow you to select from different sub-modes:

• Direct picking of the object nearest to the mouse. As you hover the mouse over the view, an arrow will appear from the furthest corner, pointing to the object nearest to the cursor. A circle is drawn around the object, with a radius large enough to include the cursor. As you move the mouse, the arrow may move to nearer objects. If you click, the position gets fixed, the circle disappears, until you click again to release the point. The selected object is shown in the control panel, see below.
  
  
• Selecting all objects within a rectangular shape. In this mode you need to drag the left-mouse button to create a rectangle, which surrounds the objects you would like to pick. When you release, the objects inside the rectangle will be selected. The non-selected objects will dim their colors to gray, so that the selected objects highlight. If objects, such as tracks, extend outside the rectangle boundaries, they will also highlight there. In the control panel you may now select the action Zoom into region to center and scale the view to only show the selected objects.
  
  

The control panel will show a table of picked objects, which update as you change your pick of the view. If only a single object is picked, its attributes will show in the attributes table. If multiple objects are picked, then you can select one object from the picked table to show its attributes. Doing so will cause the view to only highlight that single picked object.

The Options... button in the Picked objects table allows you to restrict the picking to certain layers and to certain HepRepTypes. The layers are shown in a list, with a checkbox if this layer is used in the picking. The HepRepTypes are shown in a tree, where checkboxes mark if types are used in picking.

The Options... button in the Attributes of picked object table allow you to limit the display of attributes to certain categories. The categories are shown in a list, with a checkbox if attributes of a category are shown.

Tree Selection

In tree selection mode, the control panel shows a tree of HepRepTypes. If you expand the tree you will find familiar names of your event and geometry. You can toggle the visibility of certain object types, by clicking on the right-most checkbox. The left most checkbox only exist if the object in the tree is a folder. It shows three states:

• Off, when all sub folders and sub nodes are invisible, or when this folder was made invisible by the user.
• Checked in gray, when some of the sub folders and sub nodes are visible.
• Checked in white, when all of the sub folders and sub nodes are visible.

This checkbox may change state depending on the state of other checkboxes. By clicking, it will either switch off or checked (in one of the two conditions depending on the sub-nodes). It allows you to hide whole subtrees at once.

The tree also has a popup menu to allow you to execute actions such as "Expand all", "Collapse all", "Show all", "Hide all" and "Invert All" for the node you clicked on when selecting the popup menu AND all nodes below that one.

Below the tree there are several other options available:

• By switching off the Apply immediately checkbox the user can make changes in the tree without applying them until he pushes the Apply button.
• By switching on the Hide below level checkbox the user can ignore certain depth of the tree, set by the level number. The result is reflected immediately in the tree, by dimming out useless checkboxes. The view will react immediately if Apply immediately is checked.

The tree is associated to the selected view.

Settings

The Settings panel allows you to change and control general settings and settings of the projection(s). Any variable may be selected from the table. For numeric variables a slider appears and a value box. You may use either to make changes to the variable. Variables can be coupled so that their maximum and minimum value may depend on another variable, or a variable may only be active after switching on a different variable.

Quality Settings

The quality settings allow the user to make the picture show better on the screen. The default settings are the best for performance, but for screen, printer and file output it may be worthwhile to switch some of these options on.

Draw Thick lines

This option will draw lines in the thickness given by the HepRep data. Especially for online presentations this may give better viewable results. When this option is off, the lines are drawn in single unit width, which gives the best interactive performance.

Fill Boxes

This option will fill symbols (hits) and some polygons (calorimeter hits) when the fill flag is switched on the HepRep data. When this option is off, all filled objects are drawn only by a surrounding line, which gives the best interactive performance.

Draw Frames

To show colored objects (hits) on top of other colored objects (tracks) it is sometimes useful to draw a thin (black) frame around them. This option will draw such a frame if the HepRep data contains information for it. The loss in performance can be dramatic, as the number of drawn objects multiplies by two and all frames are filled objects.

Anti-Alias

To smoothen curved lines and lines with non-trivial angles, you can switch on anti-aliasing, which blends the jagged edges due to pixelation into the background by choosing mid-tones between the line color and the background color. As this is a pixel-by-pixel operation it can be quite a performance loss. Future versions of Java may use hardware acceleration if available.

Use Layering

All objects are drawn in layers: hits on top of tracks on top of calorimeter hits on top of geometry. The layering may cause certain objects to disappear, when data has not been correctly layered. If you switch off layering these hidden objects may suddenly appear. There is no performance loss for having layering switched on.