Draw File Help Modify Tools Window
Instead of editing the data of some graphical objects in the corresponding dialogs, you can modify parts of these objects graphically. Since you can only modify one object type at a time, you have to select the type first by checking the corresponding item in the Modify menu. You may select one of the following:
2D objects Boundaries Expansions Field Function Nothing
Check the 2D objects… item when you want to graphically modify 2D objects, i.e., 2D expansions and 2D boundaries at the same time. OpenMaXwell will first ask whether you want to set the view plane equal to the xy plane and if you want to clear the graphic window. Note that you can encounter difficulties when modeling 2D objects if the view plane is not equal to the xy plane, especially if you have selected perspective projection with a short eye distance in the Field dialog.
Press the first mouse button down when the cursor is at the lower left corner of the desired selection area. Keep the button pressed while you move the cursor to the upper right corner. As soon as you release the button, the rectangular selection area is defined and the Data for selected objects dialog will pop up.
In the Data for selected objects dialog, you may specify the colour and connection numbers of all 2D expansions and 2D boundaries within the rectangular selection area. When you press the OK button, these data will be set.
Use the movie commands (for example, DELete CONnection …, MOVe COLour …, etc. Define and run the desired commands in the Movie dialog.) to maipulate the selected objects that were within the rectangular selection area.
Check the Boundaries… item when you want to graphically modify boundary data. OpenMaXwell will first ask whether you want to set the view plane equal to the xy plane and if you want to clear the graphic window. Note that you can encounter difficulties when modeling boundaries if the view plane is not equal to the xy plane, especially if you have selected perspective projection with a short eye distance in the Field dialog.
The geometric shape of a boundary is a so-called C-polygon. A usual polygon is a sequence of straight lines. To define a polygon in the xy plane, the coordinates of the corners need to be stored. A C-polygon is a polygon with arcs in the corners. The arcs are inserted in such a way that the derivative of the C-polygon is continuous everywhere. To define a C-polygon in the xy plane, the radii of the arcs and the coordinates of the corners need to be stored. When all radii are zero, a C-polygon is equal to a conventional polygon. A C-polygon with only one corner is a circle, a C-polygon with two corners is a line. A C-polygon can either be open or closed. If it is open, the radii of the start and end points are obsolete. If it is closed, the end point coincides with the start point and the data of the end point are not explicitly stored.
The first order derivative of a C-polygon is discontinuous at corners with zero radius and the second order derivative is discontinuous at the points between straight lines and arcs. In general, the local convergence of boundary methods is worst near those points where the lowest order derivative of the boundary is discontinuous. To improve the convergence, one can replace the C-polygon by a cubic spline approximation. For doing that, you must modify the boundary in the Boundary dialog.
Sometimes, a boundary is defined by an analytic boundary. In this case, the construction of a C-polygon that approximates the formula is not convenient. As an alternative, you can use the OpenMaXwell formula interpreter to define such boundaries in the Boundary dialog.
In addition to the boundary lines, OpenMaXwell draws auxiliary construction lines and handles when the Boundaries… item is checked. The construction lines are lines from the center of each arc to its start and end points and lines from the C-polygon corners to the start and end points of the automatically inserted arcs.
There are three types of boundary handles: Square, circle, and arrow. Squares mark the corners and the start and end points of arcs. Circles indicate the centers of arcs. Arrows indicate the orientation of the boundary line. Note that the orientation is important for defining the domain numbers on the left and right hand side of a boundary.
Handles of different boundaries or different handles of one and the same boundary can be at the same position. In this case, it might be impossible to fetch the desired handle. To obtain the desired result, several steps might be required. For example: 1) Move the undesired handle(s) to another position. 2) Fetch and manipulate the desired handle. 3) Move the undesired handle(s) back to the original position.
The two mouse buttons are used for different actions. The first one, i.e., the left mouse button is used for the actions move and insert, whereas the right button is used for deleting. Be careful with the right button! OpenMaXwell has no undo feature!
The arrow handles are drawn in the middle of each C-polygon line. These handles are insert points. Press the left mouse button when the cursor is on the arrow handle. A new corner will be inserted with radius 0. When you keep the mouse button pressed, you can move the corner to the desired location.
Press the right mouse button when the cursor is on one of the square handles of a corner to delete it.
Press the left mouse button when the cursor is on the square handle of a corner and move the mouse while keeping the mouse button pressed. Note that the handles of the corner and of the start and end points of the arc in the corner are identical when the radius of the arc is zero. In this case, the handle of the corner is inactive, the other handles are ‘dominant’. Therefore, you cannot directly move a corner with zero radius. Three steps are required for moving a corner with zero radius: 1) Modify the radius to a finite value. 2) Move the corner. 3) Modify the radius back to zero.
Press the left mouse button when the cursor is on the square handle of the start or end point of an arc. When you keep the mouse button pressed while moving the mouse, the radius of the arc will change. Note that the radius is set equal to the distance of the cursor (snapped to the grid) from the current corner.
When you move the end point of an open boundary to the location of its start point, the boundary becomes closed. Since the end points data is no longer required, the point will be erased. The same happens when you move the start point onto the end point.
A closed boundary cannot be opened graphically with any mouse action. For doing that, you must modify the boundary in the Boundary dialog.
When you click the left mouse button outside one of the boundary handles, the Insert dialog pops up. In this dialog, you can specify after which of the existing boundaries the new one should be inserted. When you press the OK button in the Insert dialog, a new boundary is set at the location of the cursor (before opening of the Insert dialog) and the Boundary dialog pops up. In this dialog, you should specify the non-graphic data of the boundary. Note that the new boundary first consists of a single point with zero radius. Change the radius and insert new corners with the left mouse button as indicated above.
You cannot modify some of the important boundary data graphically. For example, you cannot set the domain numbers of a boundary. For doing that, you must open the Boundary dialog.
Instead of selecting
Boundary…
from the
Tools menu, or pressing the boundary dialog
button 
of
the Tools
and draw dialog, you can open the
Boundary
dialog by right clicking one of the circular handles of a boundary. Note that
square handles and the circular handles of a line, i.e., of a C-polygon with two
corners, are at the same position. In this case, the square handles are
dominant.
To delete an entire boundary, open the Boundary dialog by right clicking a circular boundary handle and press the corresponding button in the dialog.
Click the left mouse button in one of the circular handles of a boundary for moving it. Keep the mouse button pressed and move the mouse to the desired position. Note that a line, i.e., a C-polygon with two corners, has no circular handles. To move a line, you must separately move both the start and the end points.
Check the Expansions… item when you want to graphically modify expansion data. OpenMaXwell will first ask whether you want to set the view plane equal to the xy plane and if you want to clear the graphic window. Note that you can encounter difficulties in the graphic modeling of expansions when the view plane is not equal to the xy plane, especially if you have selected perspective projection with a short eye distance in the Field dialog.
Expansions have only one handle. The handle is a circle at the location of the origin with a small line that indicates the orientation of the expansion.
Handles of different expansions can be at the same position. In this case, it might be impossible to fetch the desired handle. To obtain the desired result, several steps are be required. 1) Move the undesired handle(s) to another position. 2) Fetch and manipulate the desired handle. 3) move the undesired handle(s) back to their original position.
The left and right mouse buttons perform different actions. The left mouse button is used for moving and inserting expansions, whereas the right button is used for deleting. Be careful with the right button! OpenMaXwell has no undo feature!
Press the left mouse button when the cursor is outside any handles. The Insert dialog pops up. In this dialog, you can specify after which of the existing expansions the new one should be inserted. When you press the OK button in the Insert dialog, a new expansion is set at the location of the cursor (prior to opening the Insert dialog) and the Expansion dialog pops up. In this dialog, you should specify the non-graphical data for the expansion.
You cannot modify all of the expansion data graphically. For example, you cannot set the number of parameters, the type, etc. For doing that, you must open the Expansion dialog.
Instead of selecting
Expansion…
from the
Tools menu, or pressing the expansion dialog
button 
of
the Tools
and draw dialog, you can open the expansion
dialog by right clicking the handle of an expansion.
To delete an expansion, open the Expansion dialog by right clicking the expansion handle and press the Delete button in the dialog.
Check the Field… item when you want to modify the original field values in a single grid point or within an area of grid points. OpenMaXwell will first ask whether you want to set the view plane equal to the xy plane and if you want to clear the graphic window. Note that you can encounter difficulties in the graphic modeling if the view plane is not equal to the xy plane, especially if you have selected perspective projection with a short eye distance in the Field dialog.
Only the left mouse button is used, the right button has no effect.
Click the left mouse button when the cursor is near the desired field point. The Field components dialog will pop up. You can modify all components of the original field and the domain number of the field point in this dialog.
Press the left mouse button at the desired position and move the mouse while keeping the button pressed. This will create a rectangular area. When you release the button, the Field components dialog will pop up. Note that the dialog is the same as when you selected a single field point, but the selected grid area in the dialog will be different. Only the field components and the domain number of the initial point (where you pressed the mouse button down) will be displayed. You can modify all components of the original field and the domain number of the field point in this dialog. When you press the OK button, the field components and the domain numbers in all points within the selected area will become identical. Note that you can not only specify a rectangular area of the grid, but also a cubic 3D area. For doing that you can specify the minimum and maximum grid line numbers in x, y, and z directions in the Field components dialog.
Check the Function… item when you want to graphically modify function data. OpenMaXwell will first ask whether you want to clear the current graphic window and whether you want to let OpenMaXwell set the window limits for you.
To modify a value of the function that is displayed, press the left mouse button when the cursor is at the corresponding x position. Move the mouse and release the button when the function value y=f(x) is at the desired position.
When you have modified a value, both,
the old and the new values are displayed. If you want to see the new values
only, clear the window and redraw the function by pressing the buttons 
and 
in
the Tools
and draw menu.
Note that only a vertical mouse movement has an effect. When you want to modify the x value, you should remember that OpenMaXwell does not differentiate between functions and arguments. Open the Function dialog and check the numbers of the X and Y arguments. When you exchange these numbers, the previous x values become y values and can be modified.
When you have stored several functions or arguments, you can modify each of these. 1) Open the Function dialog and select the number of the desired function or argument in the Y argument box. 2) Close the dialog and select Function… from the Draw menu for redrawing the function. 3) Modify the values as indicated above.
Note that the function argument number 0 plays a special role. It is the number of the function value in the function array. This number is not explicitly stored in the array itself and cannot be modified. Especially when you modify multiple functions or arguments, it is helpful to select the X argument number 0 in the corresponding box of the Function dialog.
When you want to modify large function arrays, the density of function values can be very high if all values are displayed within the graphic window. This makes the selection of the desired values extremely difficult. In this case, you can adapt the limits xmin and xmax of the x axis in the Windows dialog appropriately. Instead of doing this, you might prefer to save the function to a file and edit the file with a text editor or another tool.
Check the Nothing item when you do not want to graphically modify anything. This will affect that data output in the Cursor position dialog!
Responsible for this web page: Ch. Hafner, Computational Optics Group, IEF, ETH, 8092 Zurich, Switzerland
Last update
17.02.2014