Entering a 3D Cartesian coordinate (X,Y,Z) is similar to entering a 2D coordinate (X,Y). In addition to specifying X and Y values, you specify a Z value using the following format:
X,Y,Z
In the illustration below, the coordinate 3,2,5 indicates a point 3 units along the positive X axis, 2 units along the positive Y axis, and 5 units along the positive Z axis.
When you enter coordinates in the format X,Y, the Z value is copied from the last point you entered. As a result, you can enter one coordinate in the X,Y,Z format and then enter subsequent coordinates using the X,Y format with the Z value remaining constant. For example, if you enter the following coordinates for a line
From point: 0,0,5
To point: 3,4
both endpoints of the line will have a Z value of 5. When you begin or open any drawing, the initial default value of Z is 0.
As with 2D coordinates, you can enter absolute coordinate values, which are based on the origin, or you can enter relative coordinate values, which are based on the last point entered. To enter relative coordinates, use @ as a prefix. For example, use @1,0,0 to enter a point one unit in the positive X direction from the previous point. To enter absolute coordinates, no prefix is necessary.
Coordinate filters are useful for creating a new coordinate location using the x-value from one location, the y-value of a different location, and the z-value of a third location. Coordinate filters operate the same way in 3D as they do in 2D. To specify a filter on the command line, enter a period and one or more of the letters X, Y, and Z. AutoCAD LT accepts the following filter selections:
After you specify the initial coordinate value, AutoCAD LT prompts you for the remaining coordinate values. If you enter .x at a prompt to enter a point, you are prompted for the Y and Z values; if you enter .xz at a prompt to enter a point, you are prompted for the Y value.
Coordinate filters are commonly used to locate the center of a rectangle and to locate the projection of a 3D point on the UCS XY plane.
Example: Using Coordinate Filters
When you enter coordinates by digitizing, the UCS Z value for all coordinates is 0. You can use ELEVATION to set a default height above or below the Z = 0 plane for digitizing without moving the UCS.