AutoCAD Basics - Section 1

3.4 Relative Cartesian Coordinates

The relative Cartesian coordinates are those that express the distances X and Y but with respect to the last point captured. To indicate to Autocad that we are capturing relative coordinates, we put an arroba to the values ​​when writing them in the command window or in the capture boxes. If in a relative Cartesian coordinate we indicate a pair of negative values, such as @ -25, -10 this means that the next point is 25 units to the left, on the X axis, and 10 units to the bottom, on the axis And, regarding the last entered point.

3.5 Relative Polar Coordinates

As in the previous case, the relative polar coordinates indicate the distance and angle of a point, but not with respect to the origin, but with respect to the coordinates of the last point captured. The angle value is measured in the same anti-clockwise direction as the absolute polar coordinates, but the vertex of the angle is at the reference point. It is also necessary to add an at sign to indicate that they are relative.

If we indicate a negative value in the angle of the relative polar coordinate, then the degrees will start counting clockwise. That is, a relative polar coordinate @50

The following sequence of coordinates, captured for the command Line, gives us the figure that we have placed in the Cartesian plane. We have numbered the points so that they are easily related to the coordinates:

(1) 4,1 (2) @3.5

(4) @2.11

(7) @2.89

3.6 Direct definition of distances

The direct definition of distances requires that we establish the direction of the line (or the next point) with the pointer and that we indicate a single value in the command window, which will be considered by Autocad as the distance. Although this method is very imprecise, it is very useful, and acquires precision, when combined with the “Ortho” and “Snap Cursor” screen aids that we will see a little later in this same chapter.

3.7 The coordinate indicator

In the status bar, in the lower left corner, Autocad presents the coordinates of the drawing area. If we are not executing any command, it presents the absolute coordinates dynamically. That is, these coordinates change as we move the cursor. If we start any drawing command and we have established the first point, then the coordinate indicator changes to show the absolute, relative, polar or Cartesian coordinates that it has configured in its contextual menu.

Turning off the coordinate indicator with the menu, in fact we are only passing it to its static mode. In this mode, it displays only the coordinates of the last set point. With each new point indicated in the creation of an object, the coordinates are updated.

 

3.8 Ortho, Grid, Mesh Resolution and Force Cursor

In addition to indicating coordinates in various ways, in Autocad we can also have some visual aids that facilitate the construction of objects. For example, the “ORTHO” button on the status bar constrains the mouse movement to its orthogonal positions, that is, horizontal and vertical.

This can be clearly seen during the execution of the already known command Line.

For its part, the “GRID” button activates, precisely, a grid of points on the screen to serve as guides for the construction of objects. While the “FORZC” button forces the cursor to stop momentarily on the screen at coordinates that can coincide with the grid. Both the “Grid” and “Snap” features can be configured in the “Tools-Drawing Settings” menu dialog, which opens a dialog with a tab called “Resolution and Grid”.

The “Resolution” determines the distribution of the points that will “attract” the cursor while we move it around the screen when the “FORZC” button is pressed. As can be seen, we can modify the X and Y distances of that resolution, so they do not necessarily have to coincide with the grid points. In turn, we can also modify the grid point density by modifying the X and Y interval values ​​of the grid. The lower the interval value, the denser the mesh, although it may reach a point where it is impossible for the program to display on the monitor.

Usually users set resolution values ​​equal to those of the mesh. If you activate these features with the buttons of the status bar, the points at which the cursor stops correspond to the points in the mesh.

These options, combined with “ORTHO”, allow the rapid drawing of orthogonal objects or with not very complicated geometries, such as the perimeters of houses. But to use them constantly, they require that the distances of the drawing be multiples of the X and Y intervals indicated in the dialog box, otherwise it is not much use activating them.

Finally, the extension of the grid that appears on the screen depends on the drawing limits that we determine with the "LIMITS" command, but this topic is the subject of the next chapter, where we study the configuration of the initial parameters of a drawing.