Multiframe allows you to control how much of the structure you wish to view at one time by use of two techniques named clipping and masking.  Clipping allows you to define a three dimensional box which encloses the part of the structure you wish to work with while masking allows you to selectively show or hide any member or group of members in the structure.

For example, suppose you wish to view the bending moment diagram for a given column line in a frame. Without clipping, the diagram is very difficult to decipher.  However, if you select the column line and then choose Clip to Selection from the Clipping sub-menu under the Edit menu, the diagram is made much clearer. Masking may be used in a similar way.  When a member is grey or hidden because of clipping or masking, it cannot be selected or moved with the mouse.

You can control the clipping of the structure in any of the two dimensional views in a window.  The clipping affects the display of graphics in the Frame, Load and Plot windows.  This means that you can use the clipping controls in a view of one window to make it easier to see the graphics in a different view of another window.  There are two types of clipping, clipping which draws the clipped out part of the frame in grey, and clipping which makes the clipped out members completely invisible.

When clipping is turned on, the clipping bars are displayed as dotted lines in the two dimensional view.  These dotted lines represent the boundaries of the clipping box.

To change the boundaries of the clipping box, and therefore change which members in the structure are visible, you can press and drag on the bars with the mouse.

If you want to move two bars simultaneously, you can press and drag on the intersection between the two bars and drag them at the same time.

The small triangles located between the clipping bar on the edges of the window indicate the drawing depth.  These can also be dragged using the mouse and to help align the drawing depth accurately the mouse will snap to objects and grids.

Usually you will find it convenient to start by choosing Clip To Frame from the Clipping menu.  This positions the clipping bars so that they lie just outside the outer boundaries of the frame.  You will then find it easy to move the appropriate bar to restrict your viewing to the part of the frame that is of interest to you.

You will also find it convenient to use the Clip To Selection command from the Clipping menu.  This will position the clipping bars so that they lie just outside the farthest extents of the currently selected joints.

If you try to move a clipping bar past the position of its opposing bar (for example, move the bottom bar up past the top bar) the opposing bar will be moved to maintain a small distance between the two.  This can be very useful when you want to move clipping from one floor to another or from one column line to another.  You can clip on the bar farthest from the direction you wish to move and drag the two bars together.

Clipping regions can be saved within Multiframe and used to restore clipping to a predefined region.  This enables the user to quickly restore clipping to a particular part of the model.  A clipped region is stored within Multiframe as Clipping Zone.

To save the current clipping region

§    Choose Save Clipping Zone…  from the Clipping submenu in the View menu

§    Enter a name to identify the saved region

§    Click the OK button

The current clipping regions can readily be restored to a region stored as a clipping zone.

Menu

Toolbar

To modify a zone

§    Choose Save Clipping Zone…  from the Clipping submenu in the View menu

Clipping zones are particularly useful when working with 3D models as separate zones can be defined for each of the 2D frames that make up the model. Each of these frames can then be quickly accessed by simply clipping to each of the zones

Masking allows you to control the visibility of the structure by selecting members and then choosing to show or hide them.  If you use the Mask To Selection command in the Masking menu, this will hide all of the members in the structure except those which are selected. If you choose Mask Out Selection, the selected members will be hidden and the remaining visible members will remain visible.

Like clipping, masking affects the display of graphics in the Frame, Load and Plot windows and can also be used in a view of one window to make it easier to see the graphics in a different view of another window.  Masking can also be grey or invisible however Multiframe will always ensure that clipping and masking both use the same display method. i.e. either both will display in grey or both will make hidden members invisible.

Masking is useful for situations where the area you wish to view is not rectangular in shape and therefore is not suitable for clipping.