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Polar Constraints


Restricting the cursor's movement on the screen can facilitate modeling on ARC+. You can use the cursor constraints to draw in a specific direction (parallel to X, Y or Z axes), as per a system defined angle (90°, 45°, 5°) or as per one or more angles that you define (36,5°, 69,3°, 342°, etc.)

There are various ways to restrict the cursor movement in ARC+. Arrow -  at the right side of the icon  (displayed by default) in the Modes toolbar gives access to various options. The cursor movement depends on Absolute Direction and Relative to Last Segment parameters defined in the Constraints section of the User Preferences dialog box (refer to Custom constraints for more details).
The options of the Modes toolbar when Absolute Direction is active:

ICONACTION
Set the Orthogonal Mode On/Off. When this icon is pressed the cursor is restricted to model parallel to one of the major axes.
Set the 45° constraint On/Off. When this icon is pressed, the cursor is restricted to draw in 45° and in relation to the general coordinates system.
Set the 5° constraint On/Off. When this icon is pressed, the cursor is restricted to draw in 5° and as per the general coordinates system.
Set theHorizontal constraint On/Off. When this icon is pressed, the cursor is restricted to follow the X axis.
Set theVertical constraint On/Off. When this icon is pressed, the cursor is restricted to follow the Y axis.
Open the dialog box Constraints to define the polar or step constraints (see Constraints below for more information).


The options of the Modes toolbar when Relative to Last Segment is active:

ICONACTION
Set the Orthogonal Mode On/Off. When this icon is pressed the cursor is restricted to model parallel to the last drawn segment.
Set the 45° constraint On/Off. When this icon is pressed, the cursor is restricted to draw in 45° and in relation to the last drawn segment.
Set the 5° constraint On/Off. When this icon is pressed, the cursor is restricted to draw in 5° and in relation to the last drawn segment.
Set theHorizontal constraint On/Off. When this icon is pressed, the cursor is restricted to follow the X axis, in relation to the last drawn segement (X axis is defined by the last drawn segment).
Set theVertical constraint On/Off. When this icon is pressed, the cursor is restricted to follow the Y axis, in relation to the last drawn segement (Y axis is defined by the last drawn segment).
Open the Constraints dialog box to define the polar and step constraints (see Constraints below for more information).


Custom Constraints

You can use the Polar Snap dialog box that is accessible from User Preferences dialog box to restrict the mouse movement by angle or by increment.

Additional Angles
You can use Additional Angles for Polar Snap section to specify one or more angles that the cursor will be restricted to follow. This option is very useful for the creating, measuring and editing the entities as per the angles that are used frequently in your project.
In the numerical range near the Add Angle button, enter the value of polar constraint.
Click on Add Angle button to confirm the angle selection. The angle value is displayed in the field near the Remove Angle button.
Repeat this action, as required, to add the additional angles for polar snap to the list.
NOTE: You can remove an angle at any time by selecting it in the list and clicking on Remove Angle button.

Absolute Direction option restricts the cursor to follow the specified directions in relation to the general coordinates system. For example, if the defined angles are 45° and 90°, the cursor is forced to follow these directions in relation to the general coordinates system while creating the lines.

Relative to Last Segment option restricts the cursor to follow the specified directions in relation to the last drawn segment. For the first segment of the series, the angle is in relation to thegeneral coordinates system. For example, if the angle is defined at 45°, the first line drawn will be at 45° in relation to the general coordinayes system, the second line at 45°to the first line and so on.


Click OK.
Click the  icon once again to apply your preferences to the system (icon remains pressed).
NOTE: You can deactivate the constraints at any time by clicking on  icon.

Step
Step can be used to restrict the cursor movement as per the length that you define. When this option is active, the cursor is forced to draw the segments as per the specified length (The length is measured from the given start point). A flexible line is displayed when the cursor reaches the specified value. This constraint can be used in 2D and 3D, and for lines as well as arcs.
You can activate and configure step in Polar Snap section of User Preferences dialog box. It can also be activated by using the toggle button  of Modes toolbar. You can enter a step value in the numerical range of the Modes toolbar:

NOTE: The toggle button must be pressed to activate the numerical range.
To activate set, check  checkbox of Polar Snap dialog box or click on  toggle button on Modes toolbar. checkbox and toggle button are synchronized – the parameters defined in the dialog box are displayed on Modes toolbar and vice versa.
Enter a step value (in meters) in the numerical range of the section Minimum step of moving mouse.

NOTE: The value and unit change as per the unit used.
You can use this option to control the tooltip display. The tooltip displays the number of steps taken by the cursor. For example, when the defined length of step is 5.6 meters, the tooltip displays number 1 (for one step) when the flexible line reaches a length of 5.6 meters, 2 (for two steps) when the flexible line reaches a length of 11.2 and so on.

Coordinates toolbar displays the length of the segment (in the unit used) and the angle that it makes. In the following example the defined length is 5.6 meters and the segment is of two steps length – 11.2 meters (2x5.6 meters = 11.20 meters). As per the system settings, the value displayed in Coordinates toolbar is 11.200 (meter and three decimals). The angle is 8.62.

Click on Apply and then on OK.

Snap is inhibited when step is on; the flexible direction corresponds to the available snap points and the snap markers are displayed, but the cursor is forced to follow the defined step length. The flexible line passes "through" the snap points - unless they are at the end of the step length (calculated from the last entered point).
DS Option
A new keyboard input can be used directly to define the number of steps you want to take as per the step value in use. For example, for a step value of 5.6 meters, DS 4 input defines a flexible segment of 22.4 meters (5.6 meters x 4 steps = 22.4 meters) DS command can be activated at any time, and it is independent of Step on/off checkbox and toggle button .
NOTE: The functioning of DS options is similar to that of the DL function.
Temporary Deactivation of Snap
During your work, you can deactivate the snap temporarily keeping the snap mode active and your snap preferences in force. To do this, press the Alt key and continue using the mouse as usual. When the Alt key is pressed, the cursor remains on the point you specify and does not consider the snap options selected - as if the snap was not active. You can keep the Alt key pressed as long as required to continue working without snap.