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How to work with librecad. Basics of automatic positioning and creation of primitives

In this article, we will introduce the basic concepts of QCAD and learn the basics of drawing. The article is written in such a way that the reader gradually gains the necessary knowledge. As you progress, you will come across small tasks designed to help you master QCAD. At the end of the article, an exercise will be discussed to create a simple sketch, which will allow you to consolidate the acquired skills.
>> To the table of contents of the series of articles “Mastering QCAD and LibreCAD”.

About the series of articles

This series of articles is intended for a wide audience, from a beginner getting acquainted with CAD drawing to an experienced CAD user new to QCAD. It can serve as a tutorial or tutorial in mastering QCAD.

Reasons for writing

For a Linux user, when the need arises to work with two-dimensional computer drawings, the urgent question is choosing and mastering a tool that adequately solves such problems. Unfortunately, there is currently a gap in the area of ​​working with classic 2D drawings in Linux, especially when it comes to educational materials. In this regard, I decided to devote a series of articles to teaching how to work in QCAD - one of the most developed free programs for drawing.

Why QCAD?

QCAD is one of the most advanced free programs for creating 2D drawings. For Linux, this program is a favorite in this category. QCAD has the following advantages relative to competitors such as the proprietary DraftSight:
  1. Is a free product.
  2. Feels great in the Linux ecosystem.
QCAD stores its drawings in Autodesk's open dxf format.

QCAD Logo

Installing QCAD

QCAD for your operating system can be downloaded from the official website QCAD Downloads.

What is a drawing

QCAD is used for creating digital drawings. A drawing is a model of some object, geometrically executed on a two-dimensional surface. The main differences between a drawing and a drawing are rigor, clarity and simplicity. The drawing should not be perceived as ambiguous, unlike other types of images. All this determines the basic properties of the drawings:
  1. Using a limited number of simple geometric objects (primitives) to create a drawing of an object of any complexity. Complete determinism of any drawing object.
  2. A high degree of standardization of drawing creation techniques, its main elements and their design. Using only a fixed set of lines in the drawing.

Object thinking

From a physical point of view, a classic drawing consists of two layers:
  1. Homogeneous surface (drawing sheet).
  2. Layer with drawing elements (objects).
All elements have a certain geometry and are precisely located in the drawing. Thus, they have two types of parameters - geometric structure and location (coordinates). These elements are essentially objects, and the drawing sheet is their storage.
When moving to computer drawing, the object model, which is not always noticeable in paper drawing, comes to the fore. This transition provides us with great opportunities. Now we can assign not only two types of parameters to elements, but as many as needed. In addition, it is possible to change these parameters on the fly. All this determines the greater flexibility of computer drawings compared to paper ones.

First look at QCAD

It's time to launch QCAD. When you first launch the program, you will be prompted to select the interface language and drawing settings. I prefer a white background.

Screenshot of QCAD window


Exercise: Create a new drawing in QCAD and save it with the name "Exercises" and DXF format in your drawings folder. You can then use this drawing to complete short exercises along the text.

Worksheet and navigation through it

Now let's start reviewing the options available to us. Right in the center is the drawing sheet - the main element of the program interface. Don't be alarmed by the fact that the drawing sheet in QCAD is endless. This property makes it possible to fit anything on it, thus many of the difficulties of paper drawing immediately disappear. The following quite logical navigation is possible on the sheet:
  • Moving around the sheet is done by moving the mouse while holding down the middle button
  • Scaling (zooming in or out, that is, zooming) is done by scrolling the mouse wheel

Navigation bar

An important part of the sheet is the coordinate grid. When scaling the sheet, the coordinate grid is also automatically scaled by a factor of 10. The grid nodes are evenly spaced and combined into 10x10 blocks.

Drawing sheet

Exercise: Try using drawing navigation.

Coordinate systems

The most important concept in drawing is the coordinate system. There are two types of coordinate systems in QCAD: global (absolute) and local (relative). The global coordinate system is given to us in order not to get lost on an endless drawing sheet. It serves as a kind of beacon by which we navigate on the sheet.
The local coordinate system is designed to specify the coordinates of a point relative to any location in the drawing. It can be manually moved to any convenient place.
The current cursor coordinates can be seen in the lower coordinates panel.

Coordinate panel

It shows both local and global coordinates of a point in two systems - Cartesian and polar.
You can move the local coordinate system by setting a new local coordinate zero:
Snap -> Set relative zero

Local coordinate system

Exercise: Try moving the local coordinate system to any new location in the drawing.

What is a primitive

As basic objects in QCAD, as in other CADs, so-called primitives are used - segments, circles, arcs, splines, text strings. Primitives can be assembled into more complex objects - blocks. For example, segments - into a rectangle or triangle. As we remember, objects in a drawing have two main parameters - their own geometry and location relative to other objects or the drawing sheet. Thus, when creating a primitive, you will need to define these parameters.


Some QCAD primitives and objects

First look at the toolbar and command line

The toolbar is one of the main elements of the QCAD graphical interface, and the command line is accordingly one of the main elements of the command interface. The toolbar is on the left side of the main window, and the command line is at the bottom. Next, we will master the capabilities that these interface elements provide access to, but for now we’ll just remember where they are.

Toolbar

Input focus

Transferring input focus allows you to switch between controlling the program using the graphical interface and command line. When focusing on the GUI, it is possible to use keyboard shortcuts to quick access to QCAD functions. When you focus on the command line, all keyboard input goes to it, causing the command line prompt to become of blue color. To move focus to the command line, just click on the command input field. To move the focus back to the GUI, you must press the Esc key.

Command line with input focus captured.


Exercise: Try changing input focus to the command line and back to the GUI.

Precise manual positioning

As we remember, a drawing element has two types of parameters - its own geometry and coordinate ones. The point does not have any changeable geometry of its own, so when creating a point, only the coordinates are important. To create a point, enter the command on the command line point:

point

Note: further, the need to press to enter a command after typing it will not be indicated.
We'll see that the command line prompt now says Position, which means we need to specify the coordinates to place the point. The way these coordinates are selected is called positioning. In this section we will position the point manually using direct coordinates. By default, positioning is relative to the global coordinate system. On the command line, enter the value of the x (abscissa) and y (ordinate) coordinates of the point relative to the global coordinate system, separated by commas:

You may notice that after entering the command, the command line prompt remains the same - Position . This means that QCAD's default behavior is to create new point. If we no longer need to create points, we can press the Esc key. Another interesting fact- the local origin is now located at the last point whose coordinates we specified. This rather convenient function is called automatic transfer of the relative coordinate system.
To position a point relative to the local coordinate system, use the @ symbol:

@20 , -10.5

Please note that the parameter separator is a comma, and the separator is decimal serves as a point. The use or non-use of spaces between parameters (particularly coordinates) or operators (@ symbol, comma, minus sign) does not make a significant difference. Also, do not forget that it is possible to use negative coordinates.
Positioning is possible not only in Cartesian, but also in polar coordinates:

@10<30

Here the first parameter is the polar radius p, and the second is the polar angle a(in degrees). Angles in QCAD are measured in the classic way for geometry - starting from 3 o'clock and then counterclockwise.
Exercise: Try creating multiple points using manual positioning in global and local systems coordinates

Toolbar dynamics

Anyone who carefully followed the exercises may have noticed that the contents of the toolbar do not remain constant. Indeed, the toolbar changes its content depending on our actions. Let's try to click on the second element of the panel - "Line Tools". The contents of the panel will change, providing access to a directory with functions for creating segments. To go back to more high level structure, you can press the special return key that appears at the top of the panel, or Esc on the keyboard.
Exercise: Try wandering around the nested structure of the toolbar.

Basics of automatic positioning and creation of primitives

Agree, manual positioning can be tedious. To simplify positioning, QCAD uses automatic positioning with reference to drawing objects. In the exercise where we moved the local coordinate center, we used so-called free positioning. However, free positioning is not suitable for creating a drawing. After all, as we remember, in the drawing all distances are strictly determined, and with free positioning we indicate the coordinates only approximately. Therefore, other methods are used to achieve precise positioning in the drawing.
We will begin our introduction to automatic positioning by creating a segment using two points. There are four ways to launch the function of creating such a segment:
  1. Click on the "Line Tools" button on the toolbar (the second element in a row) and select the appropriate icon.
  2. Select "Draw -> Line -> Line from 2 points" from the menu.
  3. When the English layout is on, press the “L” and “I” keys in sequence (i.e. li).
  4. Enter the command on the command line line
These four possible ways The launch of the creation of a primitive should be taken into account and the most convenient one should be chosen for use.
After activating the segment creation function, we will see that the contents of the toolbar have changed. It now provides the ability to activate some type of binding. The simplest of snaps is grid positioning. Let's select this anchor (the second element on the panel) and see how our cursor now behaves on the drawing sheet.

Grid Positioning


It turns out that we can no longer arbitrarily indicate the coordinates of a point. Instead, the cursor is drawn to the nearest grid node, thus allowing for precise positioning.
Exercise: Try creating a line segment using two points using automatic grid positioning.

Automatic binding

QCAD version 3 introduced the long-awaited automatic snapping feature. Now, the desired binding is automatically activated at a certain distance from the characteristic point. When you “capture” a point in this way, a signature of the name of the anchor appears under the cursor (in the figure below it is Middle, that is, the middle of the segment). When you click the mouse button, the point is automatically positioned according to the specified reference.
Thus, all further tasks can be performed using only automatic binding, without switching to special bindings. Automatic snapping works when the "Auto" button in the "Snap" menu is active.
I strongly recommend that you include center points in the list of automatic snaps - see the screenshot of the settings window.

List of snaps that work automatically (you need to additionally activate snapping by centers)

Creating a protractor sketch: part 1

Finally we have come to creating the first sketch. First, let's create a new drawing named "Protractor". Here is a drawing of the protractor we will make:

Sketch of a protractor


Let's start by creating the left side of the protractor ruler. First, let's start creating a segment using two points using one of the methods indicated in the previous section. Using grid snapping, we indicate the first point of the segment in the drawing using automatic positioning. Next, enter on the command line:

Thus we created a vertical segment ( x=0).
Now let's move on to creating a horizontal segment. Press Esc twice and select Create a Horizontal Line from the toolbar. Notice the options bar that appears at the top of the main window. In it we need to indicate the length of the segment 110, and select the beginning as the anchor point.

Options panel


We use binding to the endpoints of primitives. In this case, select Snap to End to snap the segment to the end point of the vertical segment. Let's move the cursor to one of the end points and create a horizontal segment.

Binding to endpoints


To create a second horizontal line, we will use another segment construction function. Press Esc twice again and select “Parallel (with Distance)” from the toolbar. On the options panel, specify the distance as 20, the quantity as 1. Now move the cursor to the already created horizontal segment. On one side of the segment, at the distance we specify, an image of a new segment will appear. Position the cursor so that the new segment is along the right side and click the mouse button to create it.
Let's complete the protractor ruler with a segment created using a line using two points, while using the same binding at the end points. However, after specifying the first point, select Restrict Orthogonally in the toolbar in the lower group. Now we won't be able to set the second point in any way other than orthogonal to the local origin. This feature is useful when drawing horizontal and vertical lines. After creating the segment, do not forget to turn off the orthogonality restrictions (Restrict Off).

Creating a protractor sketch: part 2

Great, the first part of the job is done. Let's move on to creating the protractor arc. To do this, we will use the construction of an arc based on the center, point and corners (you can find it in the arc section of the toolbar).

Toolbar with primitive sections


After initializing the creation of an arc, a prompt appears in the command line to enter “Center” (specify the center). As can be seen from the protractor drawing, the center of the arc is located in the middle of the upper side of the ruler. To position the center in this way, use the “Snap to Middle” center snap. Move the cursor to the area of ​​the middle of the upper segment and when it sticks to the center of the segment, click the mouse button to fix the center. The command line prompt will change again - it will now prompt you to specify a radius. According to the above drawing, the radius of the minor arc is 30 mm, so let's enter it into the console:
Now you will need to alternately enter the start and end angles (0 and 180 degrees, respectively). After creating the first arc, QCAD will prompt you to specify the center of the new arc.

Positioning the center of the arc


This suits us - we again indicate the same point as the center.
Then enter a radius of 50 mm. To diversify the creation process a little, we will indicate the angles using automatic snaps. To do this, we use endpoint binding (End). Now move the cursor to the upper right corner of the protractor ruler and indicate the first angle of the arc. Similarly, we define the second angle by indicating the upper left corner of the ruler. Please note that the arc is built counterclockwise from the starting angle to the ending one.

Specifying the starting angle of an arc


That's it, the sketch is ready! You can download my sketch.

Conclusion

In this article we looked at the basics of working in QCAD and learned how to make simple sketches. The next article will look at the techniques needed to create complete drawings. Based on the developments we already have in the form of a sketch of a protractor, we will begin creating a complete drawing of this object.

Until LibreCAD has not completely transferred all the features of the QCAD community edition, we will use QCAD. And periodically test LibreCAD for speed.

Table of Contents

Story

There is a company called RibbonSoft that produces CAD and CAM programs. It has a QCAD product and the company releases separately QCAD Community Edition - this is the previous version of QCAD with code under GPLv2. But it so happened that about 2 years ago, distributions gradually began to move from the Qt3 graphical toolkit on which QCAD-CE 2 (hereinafter referred to as QCAD2) is written, to Qt4 because of this it became increasingly difficult to run QCAD on new distributions. Also, new versions were not released, and so a group of enthusiasts created a project to transfer QCAD code to Qt4 and they called it CADuntu, then it was decided to rename it LibreCAD. They ported the code, made it work and even included what was missing in QCAD2, view the documentation. After which we received a ban from RibbonSoft from using the manual, fonts when installing LibreCAD, the problem with the fonts was solved, but the manual has not yet been rewritten.

As time passed, new designs appeared in LibreCAD, new tools, such as ellipses. The apogee was the implementation of multiple bindings (by default, only one binding works in QCAD2) and the ability to connect plugins. Then activity in the project died down or went to fight with FSF over the LibreDWG license

Sudo apt-get install librecad

In Gentoo you will most likely need to enable overlay

Ubuntu PPA

PPA is a developer repository with the latest versions of programs, allowing you to combine stable systems and some fresh third-party software.

Sudo add-apt-repository ppa:librecad-dev/librecad-daily sudo apt-get update sudo apt-get upgrade sudo apt-get install librecad

Build from source codes

Let's install the prerequisites: Qt4-dev libraries, a parser and the recently released boost libraries.

Sudo apt-get install g++ gcc make git-core libqt4-dev qt4-qmake\ libqt4-help qt4-dev-tools libboost-all-dev libmuparser-dev\ libfreetype6-dev

Now download the latest version of Librecad and compile it

Mkdir -p source cd source git clone https://github.com/LibreCAD/LibreCAD cd LibreCAD qmake librecad.pro make

When to look at plugins

Cd LibreCAD cd plugins qmake make cd .. qmake librecad.pro make

Cd unix ./librecad

Key Features

Let's consider the purpose of program elements:

  • 1 — Here we are drawing a working field.
  • 2 — Basic tools, practically not much different from QCAD
  • 3 — Bindings, here we activate them ourselves, there is no smart selection of the nearest binding... and unlike QCAD2, you can enable several bindings at once.
  • 4 — When there is a frequently repeated object in a drawing, especially in architectural drawings, it is drawn, then a block is created, and then moved and inserted, saving memory and the size of the drawing file.
  • 5 — Manual selection of line style and thickness for selected objects
  • 6 — Layers themselves allow you to separate objects; objects created on a layer initially have the style attributes of this layer. When you start a new drawing, you only have the zero layer, which you will not delete and on which you will have to drop all other layers if you want to open your dxf in a program that does not support layers in dxf, or when you delete a layer, all objects in the layer are moved to 0.( Layers with only Latin names)
  • 7 — Template library. There are also frequently repeated templates, such as drawing formats, schematic images of electrical appliances, etc., for which it is convenient to use this library.
  • 8 — Command line, convenient when you need to enter exact values, it works in parallel so you can switch to it by pressing SPACEBAR

Tricks


QCAD

A few words about QCAD2

If you are an oldstable fan and a necrophile, you might want to decorate your qt3 interface, for this use the package polymer

Installing QCAD Community Edition

That's why I haven't seen any packages or PPAs for it.

True, we installed Qt4 using the system utility.

LibreCAD is one of the most developed free scribers. For the Linux operating system, this program is, in my subjective opinion, the favorite in this category based on the sum of criteria. LibreCAD arose not so long ago as a fork of the free implementation of the commercial scriber QCAD, due to the fact that the development of the latter had slowed down. LibreCAD has the following advantages relative to competitors such as the proprietary DraftSight:

  1. It is a completely free product.
  2. Feels great in the Linux ecosystem.

LibreCAD differs from the free QCAD community edition in the following ways:

  1. It has a nice interface based on Qt4.
  2. It is actively developing at the moment.

LibreCAD stores its drawings in the open dxf format from Autodesk.

Installing LibreCAD

LibreCAD is available in the repositories of many distributions. Installing LibreCAD on ububtu is easy:

sudo apt-get install librecad

Information about installing LibreCAD on your OS can be found on the official website. This article discusses LibreCAD version 1.0.1.

What is a drawing

LibreCAD is used for creating digital drawings. It is impossible not to note what this is all about. A drawing is a model of some object, geometrically executed on a two-dimensional surface. The main differences between a drawing and a drawing are rigor, clarity and simplicity. The drawing should not be perceived ambiguously, unlike other images. All this determines the basic properties of the drawings:

  1. Using a limited number of simple geometric objects (primitives) to create a drawing of an object of any complexity. Complete determinism of any drawing object.
  2. A high degree of standardization of drawing creation techniques, its main elements and their design. Using only a fixed set of lines and hatches/fills in a drawing.

Object thinking

From a physical point of view, a classic drawing consists of two layers:

  1. Homogeneous surface (drawing sheet).
  2. A layer with drawing elements drawn, for example, with a pencil.

All elements have their own geometry and are somehow located in the drawing. Thus, they have two types of parameters - geometric structure and location (coordinates). Therefore, these elements are essentially objects, and the drawing sheet is their storage.

When moving to computer drawing, the object model, which is not always noticeable in paper drawing, comes to the fore. And such a transition provides us with great opportunities. Now we can assign not only two types of parameters to elements, but as many as needed. In addition, it is possible to change these parameters on the fly. All this determines the unprecedented flexibility of computer drawings compared to paper ones.

First look at LibreCAD

Well, let's take a break from the theoretical aspects for a moment. It's time to launch LibreCAD. At the first launch, we will most likely see a black drawing canvas with white dots applied to it. The dots here play the same role as the lines in a checkered notebook - they allow you to more accurately position the elements of the drawing relative to each other. Otherwise, the main program window looks very similar to the window of any other average program - it has a main menu, a toolbar, and various additional panels. We will return to all this later.

First, a small technical point. I personally prefer a white drawing sheet background. If you also want to change the background from the default black to white, this can be done as follows: Edit -> Program Settings -> Appearance-> Colors -> Background: #ffffff

Exercise: Create a new drawing in LibreCAD and save it with the name "Exercises" and DXF format in your drawings folder. You can then use this drawing to complete short exercises along the text.

Worksheet and navigation through it

Now let's start reviewing the options available to us. Right in the center is the drawing sheet - the main element of the program interface. Don't be alarmed by the fact that the drawing sheet in LibreCAD is endless. This property makes it possible to fit anything on it, thus many of the difficulties of paper drawing immediately disappear. The following quite logical navigation is possible on the sheet:

  • Moving around the sheet is done by moving the mouse while holding down the middle button
  • Scaling (zooming in or out, that is, zooming) is done by scrolling the mouse wheel

Navigation bar

An important part of the sheet is the coordinate grid. When scaling the sheet, the coordinate grid is also automatically scaled by a factor of 10. The grid nodes are evenly spaced and combined into 10x10 blocks.

Drawing sheet

Exercise: Try using drawing navigation.

Coordinate systems

The most important concept in drawing is the coordinate system. There are two types of coordinate systems in LibreCAD: global (absolute) and local (relative). The global coordinate system is given to us in order not to get lost on an endless drawing sheet. It serves as a kind of beacon by which we navigate on the sheet.

The local coordinate system is designed to specify the coordinates of a point relative to any location in the drawing. It can be manually moved to any convenient place. The current cursor coordinates can be seen in the lower coordinates panel.

Coordinate panel

It shows both local and global coordinates of a point in two systems - Cartesian and polar. You can move the local coordinate system by setting a new local coordinate zero: Snap -> Set relative zero

Local coordinate system

Exercise: Try moving the local coordinate system to any new location in the drawing.

What is a primitive

As basic objects in LibreCAD, as in other CADs, so-called primitives are used - segments, circles, arcs, splines, text strings. Primitives can be arranged into more complex objects - blocks, for example segments - into a rectangle or triangle. As we remember, objects in a drawing have two main parameters - their own geometry and location relative to other objects or the drawing sheet. Thus, when creating a primitive, you will need to define these parameters.

First look at the toolbar and command line

The toolbar is one of the main elements of the LibreCAD graphical interface, and the command line is, accordingly, one of the main elements of the command interface. The toolbar is on the left side of the main window, and the command line is at the bottom. Next, we will master the capabilities that these interface elements provide access to, but for now we’ll just remember where they are.

Input focus

Moving input focus allows you to switch between controlling the program using the graphical interface and the command line. When focusing on the GUI, it is possible to use keyboard shortcuts to quickly access LibreCAD functions. When you focus on the command line, all keyboard input goes to it, causing the command line prompt to turn blue. To move focus to the command line, just click on the command input field. To move the focus back to the GUI, you must press the Esc key.

Command line with input focus

Exercise: Try changing input focus to the command line and back to the GUI.

Precise manual positioning

As we remember, a drawing element has two types of parameters - its own geometry and coordinate ones. The point does not have any changeable geometry of its own, so when creating a point, only the coordinates are important. To create a point, enter the point command on the command line: point

We will see that the command line prompt now says “Specify location”, which means we need to specify the coordinates of the location of the point. The way these coordinates are selected is called positioning. In this section we will position the point manually using direct coordinates. By default, positioning is relative to the global coordinate system. Enter in the command line, separated by commas, the value of the x (abscissa) and y (ordinate) coordinates of the point relative to the global coordinate system: 10,10

You may notice that after entering the command, the command line prompt remains the same - “Specify location”. This means that LibreCAD's default behavior is to create a new point. If we no longer need to create points, we can press the Esc key. Another interesting fact is that the local origin is now located at the last point whose coordinates we specified. This rather convenient function is called automatic transfer of the relative coordinate system.

To position a point relative to the local coordinate system, use the @ symbol: @20, -10.5

Please note that the parameter separator is a comma, and the decimal separator is a period. The use or non-use of spaces between parameters (particularly coordinates) or operators (@ symbol, comma, minus sign) does not make a significant difference. Also, do not forget that it is possible to use negative coordinates.

Positioning is possible not only in Cartesian, but also in polar coordinates: @10 Here the first parameter is the polar radius p, and the second is the polar angle a (in degrees). Angles in LibreCAD are counted in the classic way starting from 3 o'clock and then counterclockwise. Exercise: Try creating multiple points using manual positioning in global and local coordinate systems.

Toolbar dynamics

Anyone who carefully followed the exercises may have noticed that the contents of the toolbar do not remain constant. Indeed, the toolbar changes its content depending on our actions. Let's try to click on the second element of the panel - "Show menu Lines". The contents of the panel will change, providing access to a directory with functions for creating segments. To go back to a higher level of the structure, you can press the special return key that appears at the top of the panel, or Esc on the keyboard. Exercise: Try wandering around the nested structure of the toolbar.

Basics of automatic positioning and creation of primitives

Agree, manual positioning can be tedious. To simplify positioning, LibreCAD uses automatic positioning with reference to drawing objects. In the exercise where we moved the local coordinate center, we used so-called free positioning. However, free positioning is not suitable for creating a drawing. After all, as we remember, in the drawing all distances are strictly determined, and with free positioning we indicate the coordinates only approximately. Therefore, other methods are used to achieve precise positioning in the drawing.

We will begin our introduction to automatic positioning by creating a segment using two points. There are four ways to launch the function of creating such a segment:

  1. Click on the "Show menu Lines" button on the toolbar (the second element in a row) and select the appropriate icon.
  2. Select "Drawing -> Line -> 2 points" from the menu.
  3. When the English keyboard layout is on, press the “l” and “i” (i.e. li) keys in sequence.
  4. Enter the line command at the command line

These four possible ways to start creating a primitive should be taken into account and the most convenient one should be chosen to use. After activating the segment creation function, we will see that the contents of the toolbar have changed. It now provides the ability to activate some type of automatic binding. The simplest of snaps is grid positioning. Let's select this anchor (the second element on the panel) and see how our cursor now behaves on the drawing sheet.

Grid Positioning

It turns out that we can no longer arbitrarily indicate the coordinates of a point. Instead, the cursor is drawn to the nearest grid node, thus allowing for precise positioning. Exercise: Try creating a line segment using two points using automatic grid positioning.

Creating a protractor sketch: part 1

Finally we have come to creating the first sketch. First, let's create a new drawing named "Protractor". Here is a drawing of the protractor we will make:

Sketch of a protractor

Let's start by creating the left side of the trasporter ruler. First, let's start creating a segment using two points using one of the methods indicated in the previous section. On the toolbar, select grid snapping and indicate the first point of the segment in the drawing using automatic positioning. Next, enter on the command line: @0.20

Thus we created a vertical segment (x=0).

Now let's move on to creating a horizontal segment. Press Esc twice and select Create a Horizontal Line from the toolbar. Notice the properties panel that appears at the top of the main window. In it we need to indicate the length of the segment - 110, and select the beginning as the anchor point.

Properties panel

We use a new type of binding - binding to points on primitives. In this case, select Snap to endpoints to snap the segment to the end point of the vertical segment. Let's move the cursor to one of the end points and create a horizontal segment.

Binding to endpoints

To create a second horizontal line, we will use another segment construction function. Press Esc twice again and select “Parallel at a distance” from the toolbar. On the properties panel, specify the distance as 20, the quantity as 1. Now move the cursor to the already created horizontal segment. On one side of the segment, at the distance we specify, an image of a new segment will appear. Position the cursor so that the new segment is on the desired side and click the mouse button to create it.

Let's complete the protractor ruler with a segment created using a line using two points, while using the same binding at the end points. However, after specifying the first point, select the orthogonally restriction (restrict orthogonally) in the toolbar in the lower group. Now we won't be able to set the second point in any way other than orthogonal to the local origin. This feature is useful when drawing horizontal and vertical lines. After creating the segment, do not forget to turn off restrictions.

Creating a protractor sketch: part 2

Great, the first part of the job is done. Let's move on to creating the protractor arc. To do this, we will use the construction of an arc based on the center, point and corners (you can find it in the arc section of the toolbar).

Toolbar with primitive sections

After initializing the creation of an arc, the prompt “Specify center” appears in the command line. As can be seen from the protractor drawing, the center of the arc is located in the middle of the upper side of the ruler. To position the center in this way, select the snap to center points. Now move the cursor to the area of ​​the middle of the upper segment and when it sticks to the center of the segment, click the mouse button to fix the center. The command line prompt will change again - it will now prompt you to specify a radius. Well, according to the drawing above, the radius of the minor arc is 30 mm, so we enter it: 30

Now you will need to alternately enter the start and end angles (0 and 180 degrees, respectively). After creating the first arc, LibreCAD will prompt you to specify the center of the new arc.

Positioning the center of the arc

This suits us - we again indicate the same point as the center. Then enter a radius of 50 mm. To add some variety to the creation process, let’s specify the angles using automatic snaps. To do this, select binding by endpoints. Now move the cursor to the upper right corner of the protractor ruler and indicate the first angle of the arc. Similarly, we define the second angle by indicating the upper left corner of the ruler. Please note that the arc is built clockwise from the starting angle to the ending one.

Specifying the starting angle of an arc

Well, the sketch is ready! You can download my sketch.

Conclusion

In this article, we looked at the basics of working in LibreCAD and learned how to make simple sketches. The next article will look at the techniques needed to create complete drawings. Based on the developments we already have in the form of a sketch of a protractor, we will undertake the creation of a complete drawing of this object.