User Coordinate Systems

When you create entities in a drawing, they are located in relation to the drawing's underlying Cartesian coordinate system. The ELEVATION system variable specifies the distance from the xy-plane of the current coordinate system. If ELEVATION = 0 (zero), entities are created in the xy-plane of the current coordinate system.

Every drawing has a fixed coordinate system called the World Coordinate System (WCS).

You can also define arbitrary coordinate systems located anywhere in three-dimensional space. These are called user coordinate systems (UCS) and can be located anywhere in the WCS and oriented in any direction. You can create as many UCS as you want, saving or redefining them to help you construct three-dimensional entities. By defining a UCS within the WCS, you can simplify the creation of most three-dimensional entities into combinations of two-dimensional entities.

When you create a new drawing the WCS is the current coordinate system by default, which is indicated by the letter W in the UCS icon. When you display a drawing in plan view, you see the coordinate system icon from the top, with the z-axis directed straight toward you. When you display a three-dimensional drawing in a view other than plan view, the coordinate system icon changes to reflect your new viewpoint.

To help you keep your bearings in the current coordinate system, BricsCAD displays a coordinate system icon (UCS icon). The visible portions of the axes are the positive directions.

Three colors represent the three axes, making it easier for you to recognize the orientation in three-dimensional space:

• x-axis: red

• y-axis: green

• z-axis: blue

The colors of the axes are controlled by the COLORX, COLORY and COLORZ system variables.

The Plan View command restores the Plan view or Top view of the current UCS or WCS.

The UCSICON settings variable controls the display and location of the UCS icon:

Show icon :

Controls whether the icon shows or not.

at origin :

Controls the location of the UCS icon: if on, the icon indicates the origin point of the current coordinate system (UCS or WCS). However, if the origin is not within the viewport borders, the UCS icon moves to the corner of the viewport, as defined by the UCSICONPOS (UCS Icon Position) settings variable.
When the at origin option is not checked, the icon always displays in the corner of the viewport defined by UCSICONPOS.

To move the origin of the current coordinate system

1. Type ucs at the command prompt.
   You are prompted: Specify origin of UCS or [Face/NAmed/Entity/Previous/View/X/Y/Z/Z Axis/Move/World] <World>:

2. Identify the new origin, then press Enter to confirm.

To define a User Coordinate System

1. Choose Drawing Explorer > Coordinate Systems in the Tools menu.
   The Drawing Explorer - Coordinate Systems dialog opens.
2. Click the New tool button () on the Drawing Explorer dialog.
   The BricsCAD Explorer dialog closes.
   You are prompted: Current/Entity/Origin/View/X/Y/Z/ZAxis<3point>:
   A prompt menu displays:
   
   
3. Press Enter to define the UCS using points.
   You are prompted: New origin <current origin>:
4. Specify the origin point of the UCS.
   You are prompted: Point of positive X axis <current point>:
5. Specify a point to define the positive X-axis.
   The command window reads: Point in X-Y plane with positive Y value <current point>:
6. Specify a point to define the positive Y-axis.
   The UCS is defined.
   The BricsCAD Explorer dialog reopens.
7. Click in the UCS Name field of the newly defined UCS to replace the <NewUCS> default name.
8. Close the BricsCAD Explorer dialog.

Command Options

See the EXPUCS and UCS commands.

To restore the WCS

1. Type UCS in the command bar, then press Enter.
   You are prompted: ?/3point/Delete/Entity/Origin/Previous/Restore/Save/View/X/Y/Z/Zaxis/<World>:
   A prompt menu displays.
2. Do one of the following:
3. Press Enter to accept the default option.
4. Choose World in the prompt menu.
5. Type W in the command bar and press Enter.

To restore a UCS

1. Choose Drawing Explorer > Coordinate Systems in the Tools menu.
   The Drawing Explorer - Coordinate Systems dialog opens.
2. Click the blank tile in front of the UCS name to make it current.
   
   
3. Close the BricsCAD Explorer dialog.

To set a relative UCS

1. Do one of the following:

• Click the UCS... tool button () on the Settings toolbar.
• Choose UCS... in the Settings menu.

The User Coordinate System dialog opens.

2. Choose one of the following:

• Set the selected UCS relative to the Current UCS .
• Set the selected UCS relative to the World coordinate system (WCS) .

3. (option) Enable the Change view to plan view of the selected UCS option.

4. Click one of the Planar UCS's buttons.
The User Coordinate System dialog closes.

Command Options

See the SETUCS command.

Dynamic UCS (DUCS)

With the Dynamic UCS feature enabled, the coordinate system is aligned automatically with a face of a 3D solid under the cursor when drawing entities.

This feature is controlled by the UCSDETECT system variable.

The RedHilite_DUCSLocked_Face_Color user preference controls the highlight color for the face to which the Dynamic UCS has been locked by pressing the Shift key.

The RedHilite_DUCSLocked_Face_Alpha user preference controls the highlight transparency for the face to which the Dynamic UCS has been locked by pressing the Shift key.

To toggle the dynamic UCS

Do one of the following:

• Press the F6 function key.
• Click the DUCS field in the status bar.

Using the Dynamic UCS

1. With the Dynamic UCS feature active, launch a Draw command.
2. Move the cursor over the face of a 3D solid.

• The face highlights.
• If ON, the grid is aligned with the selected face.
• If the UCSICON system variable = 3 (On at Origin), the UCS icon displays in the selected face.
• The dynamic UCS is oriented according to the edge by which the cursor 'entered' the hovered face, thus providing users a way to manipulate the orientation of the DUCS. The origin of the DUCS is set to the start point of this edge and the X-axis is chosen codirectional to the tangent at the start point of the edge.

3. (option) Hit the Shift key to lock the DUCS, which allows you to start drawing outside the highlighted face.
Hit the Shift key again to unlock the DUCS.

4. Pick a point to start drawing.

5. When the drawing command concludes, the WCS or previously defined UCS is restored.