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Installing and Using Construction Lines For Blender

Construction Lines - DND Site.jpg

Note: This add-on requires Blender 2.8 or higher ( This tutorial was made using Blender 2.83 so some screenshots and menus may differ slightly if you use a different version


Download Construction Lines Add-on

Keys: Alt+' = Shortcut to start Construction Lines,  T = Tape Measure, L = Line Drawing,  R = Rectangle Drawing,  C = Circle Drawing,  U = Arc Drawing, G/M = Move Object, H = Hide/Show Guides, DEL = Remove All Guides 

Overview And Key Functions

Construction Lines is a tool for accurate CAD style modelling. Build snappable guide points and guide edges, draw lines and primitive shapes in place, automatically create faces in closed geometry and precisely move object geometry around a scene. The tool is designed for CAD style drawings but works just as well with any other type of modelling.


Guide edges and points allow for a construction workflow where guides are set and models are then constructed within these guides. The guides won't interfere with model geometry and can be toggled off and on when required. Guides edges will disappear when working outside of Construction Lines and neither Guide Edges nor Guide Points will be rendered. 


Construction Lines allows for rectangles, circles, and arcs to be drawn in place from precise snap points on existing geometry or guides. These can be drawn from anywhere on a 3D model without the need for Blender's 3D cursor to define an Add location. They can also be drawn onto existing geometry and automatically cut into existing faces.


Construction Lines works seamlessly between Object and Edit modes in Blender.

NB. Construction Lines is currently in Beta and is regularly updated with fixes and improvements.


  1. Installing Construction Lines

  2. Starting Construction Lines

  3. Environment Setup

  4. Measuring And Setting Guide Edge/Points

  5. Guide Conversion

  6. Notes On Snapping

  7. Modeling With Construction Edges And Guides

  8. Drawing Lines And Faces

  9. Splitting Faces And Edges With Lines

  10. Drawing Shapes In Place (Rectangles, Circles & Arcs)​

  11. Drawing Shapes To Exact Size

  12. Drawing On Existing Geometry

  13. Precise Object Movement

  14. Advanced Measurement And Guide Setting

  15. Create Face

  16. Exiting Construction Lines and Cancelling Operations

  17. Extra Tips And Tricks


Installing Construction Lines


Once you've downloaded the Construction Lines .zip file*, open Blender

  1. Navigate to Edit->Preferences which will open a Preferences dialog

  2. Click Add-ons in the left-hand buttons. Click the Install… button and find the downloaded .zip file.

  3. Press Install Add-on from File. This will install the add-on.

  4. To activate it click the checkbox where you see the 3D View: Construction Lines item (see below image).

  5. You can now exit the Preferences Dialog.

* Please note that some buying platforms deliver the Construction Lines .zip in their own .zip file. Please make sure that the installation .zip is of the format "Construction" where the # are the version numbers.

** If any errors are displayed on starting Construction Lines, please restart Blender and try again.

Construction Lines Addon Menu

Starting Construction Lines


Construction Lines can be used in either Object or Edit mode. Simply select the Construction Lines tool from the tool palette on the left-hand side of the 3D view window (in either Object or Edit mode). If the tool palette is not visible press 'T' to display.

Starting Construction Lines

Construction Lines

Tip: For quick access Construction Lines can be accessed with the Alt+` (NB. This is the Accent Grave key normally found beside the number 1 on the top row of a keyboard, not the apostrophe key). Right-clicking the Construction Lines tool icon and selection Add To Quick Favorites will also allow for quick access to the tool when 'Q' is pressed.


If Construction Lines has started correctly the cursor in the modeling view will have a small yellow dot below it. 

Right-Clicking will display a context menu with all of the Construction Line operations.


Tape - Measuring and guide creation

Line - Draw lines with auto face creation

Rectangle - Draw a rectangle

Circle - Draw a circle

2 Point Arc - Draw an arc with a start, endpoint and height

Move - Precise snapped object movement

Create Face - Create a face from any selected points

Convert To Geometry - Converts a Guide Edge to real geometry (hold Shift to select guide)

Hide/Show All - Hide and show all Guides

Scale All - Scale existing guide points based on the preference scale

Remove All - Remove all Guides

Exit - Exit Construction Lines  

Environment Setup


Construction Lines works with all Blender measurement unit types. To change unit type click on Scene Properties in the Properties Editor (right-hand side of the workspace view. See below image) and expand Units. Select the preferred system under the Unit System and select units under Length.

Environment Setup

Tip: For ease of use it's best to choose smaller units, so that whole numbers can be used rather than fractions. If working in metric it's a good idea to use Millimeters instead of Meters and Inches\Thou instead of Feet if working in Imperial.

Measuring And Setting Guides

Measuring And Setting Guide Edge/Points

Taking measurements is a key Construction Lines operation. The measure/guide building tool is the default operator when starting Construction Lines. Move the cursor around the 3D view to snap to a point (this may be the 3D cursor in an empty scene), clicking once will set a starting point. Dragging the cursor around the view will show a dashed line that represents the measuring tool length. The distance on all axes are displayed in the info bar at the top of the view (see below image). An overall distance in 3D space is also displayed (Distance, dx, dy, and dz). 


If units have been set up in Scene Properties these will be displayed at the end of any value.

Tip: You can change the scale of guide points in the add-on preferences menu (see notes at bottom of page)


Measurement Display

Guide points can be set by making a second clicked. This will create two new guide points, one at the start and one at the end of the guide. A construction edge is also created. The guide points and edge are now snappable, so they can be used for snapping new measurements, geometry addition, or moving objects to a precise location. 


Clicking once and dragging, then pressing the Enter key will enter numeric input mode. Type in a distance and press Enter again, this will extend the measurement in the same direction by that exact amount. 


Pressing X, Y, Z keys will allow the measurement to be locked on a single axis. Construction Lines will also temporarily auto-lock to an axis if dragging gets close to it (see auto snapping). The below image shows the colour change to blue when the axis lock is set to Z-axis.


You can add divide between guide points by hold Ctrl and scrolling the mouse wheel (or pressing the up/down keys), this will equally divide the guide edge by the set number of divisions. Clicking again to set the end of the measurement will create the start and endpoints to the guide edge and also create new guide points at the points of division.  

Guide Conversion


Guide edges can only be used whilst working with the Construction Lines tool. Once you exit Construction Lines, the guide points will remain but guide edges will disappear as these are a Construction Lines specific feature. If you want to use guide edges with other Blender tools and in normal Blender operation, you can simply convert a guide edge or edges to real Blender geometry.


Whilst in Construction Lines select the guide edge you wish to convert by holding Shift and clicking on the guide edge. The edge will now turn Orange to show that it is selected. Holding Shift you can select multiple edges. Now right-click for the Context Menu and select Convert To Geometry this will convert the guide edges to Blender edge geometry.  


Guide Conversion

Guide Edges

Shift + Click to Select


Convert to Geometry


Guide Is Now A Blender Edge


Notes On Snapping


As the cursor snaps to various parts of the blender geometry or Construction Lines guides, the highlighted snap point changes colour.  


Green = Vertex

Dark Blue = Edge

Purple = Edge Center

Light Blue = Face

Direction Snapping

Construction Lines will automatically snap to global axes directions (X, Y, Z) and also to directions that are perpendicular to an edge, or in a direction that extends an edge. Direction snapping works even whilst drawing onto existing geometry. 

Tip: Holding down alt whilst moving or dragging will temporarily disable snapping


Pink = Perpendicular To Edge

Purple = Extends Edge

Modeling With Construction Edges And Guides 

Using constructions guides in modeling is a very powerful tool for building accurate models. It allows you to plan out a model before building and to calculate positions without needing to build any geometry.

Construction Lines are also useful for snapping objects into position. Once a construction line is created, new geometry or objects can be snapped to it.

Modelling With Guides

Guide Snapping

Drawing Lines And Faces

Fundamental to any CAD modeling is the ability to draw lines/edges. Construction Lines allows for continuous lines to be drawn. These are handled in the exact same way as Measurements (make sure to select the line tool in the context menu or press the 'L' key), by clicking a snapped starting point, dragging to the desired end location and clicking for a second time to finish.


A new line will automatically continue from where the previous line has finished. Pressing the Esc key will cancel this action. 

Drawig Lines And Faces

Once Construction Lines discovers a closed face in the newly drawn lines, it will automatically create a new face, without the need for any user input. 


Lines can also be extended in the current direction with the mathematical operators (+, -,  /, *). This is the same for the measurement tool (see Advanced Measurements And Guides section below).

Tip: The Line Tool requires all points to be coplanar if it's to automatically create a face, in scenarios where points are not coplanar it may be easier to use the Create Face tool (see below) 

Splitting Faces And Edges With Lines

Existing faces can be split using the line tool. Select a face in Edit mode and draw a line across the face, from one edge to another in the face. The connected edges and face will automatically be divided. Operations can now be performed on the two separate faces (extrude, etc.)

Splitting Geometry

Drawing Shapes In Place (Rectangles, Circles & Arcs)

A very powerful feature of Constructions Lines is the ability to draw shapes, starting from any point on a mesh/object. Simply choose the desired shape from the Construction Lines context menu or use the R, C, and U shortcut keys (Rectangle, Circle, and Arc), snap to a starting point anywhere on an object mesh or guide point and drag to the required size. Just like line and Measurement tools, shapes can be locked to an axis by using the X, Y, Z keys, which will switch the orientation of the shape being drawn.


Arcs are drawn in the same way as rectangles and circles but require a third click, to define the height of the arc.

Drawing Shapes

The number of segments for an arc or circle can be adjusted by using the up and down arrows on the keyboard whilst drawing or by holding the Ctrl key and using the mouse wheel. The number of segments is shown in the top info bar.

Tip: Arcs are not built as closed geometry. To close an arc, simply select the arc in edit mode and draw a line connecting the two endpoints. Construction Lines will automatically create a new face, filling the arc in.

Drawing Shapes To Exact Size

All shapes can be drawn to a precise size by typing in a number or calculation (2*4.3, /2, etc.), once the shape has been started. Sizes for Rectangles can either be comma-delimited to define length and width, or a single number can be used to build a square. 


Drawing On Existing Geometry

As previously noted, it is possible to split faces of existing geometry by drawing a line across an existing face, in Edit mode. It is also possible to cut into existing faces with new shape geometry and add shapes to existing geometry, thus extending them. 


Drawing To Size
Drawing On Existing

Cutting into an existing face, away from an edge, is now possible (from Construction Lines version 0.9.4). Extra geometry is automatically added, which is required for Blender to correctly split the face. This allows you to draw a shape anywhere on an existing face and use the newly cut face to extrude in or out of an existing mesh/volume.

Precise Object Movement

Objects can be moved around in 3D space by snapping to and selecting an object. The object will then be dragged from this snap point. The Snap point can either be a vertex, edge, edge center, face, or a point along an edge.


Pressing G, M, or selecting Move from the context menu will allow the object to be dragged around the model view and snapped to any object or guide. This is very powerful for making precision object moves.


Object Movement

"/2" Typed Input

Advanced Measurement And Guide Setting

Measurements can also include addition, subtraction, division, or multiplication by using the +, -, / and * operations. To divide a measurement in half simply click and drag in a direction, press Enter to enter input mode, then type "/2" and hit Enter again. Typing "/3" will divide the space to a third and "/4" to a quarter. Construction Lines allows for floating-point numbers so very precise measurements can be set.


Advanced Measurement

Guide Point Half Way Along Measured Length

Create Face

Create Face


Blender has its own Create Face function, however, this only works whilst in edit mode and only from existing vertices/edges. Construction Lines allows face creation in object mode and from any snap point. Holding Ctrl and clicking any vertex or snap point (edge center, a point along edge/face, or guide edge/point) a point is highlighted red and stored for face creation. Make three or more point selections and press the F key (or select Create Face from the context menu). This will create a new face from these points and will add to the scene as a new object.  

In some scenarios, this is easier than using the Line Tool to trace the path of a face, for instance when points are not coplanar, as the line tool requires points to be on the same geometric plane before automatically creating a face.


Exiting Construction Lines and Cancelling Operations

Pressing The Esc key will cancel the current drawing operation and pressing Esc again will exit the Construction Lines altogether, returning to the default Blender Select tool. The right-click context menu also has an Exit item.

If you have the Blender tool menu open, clicking another tool will automatically exit Construction Lines.


Extra Tips And Tricks

Extra Tips And Tricks

When dragging out geometry or drawing lines, to keep everything on the same plane switch into the orthographic mode in the 3D viewport (5 on the Numpad or the grid icon below the axis gizmo) and choose a view (front, left, right, top, bottom) either from the axis gizmo or using the Numpad keys (1, 3, 7 holding ctrl to view the opposite direction). Drawing will now no longer use 3D depth and be flattened to the current plane. This is useful when drawing floorplans.

The colour of Guide edges can be changed by heading to Edit->Preferences->Add-ons and finding Construction Lines in the add-on list. Click the item to expand. Under Preferences an item named Colour Of Guides allows you to change the colour. The default colour is RGB(0.3, 0.3, 0.3)

The scale of Guide points can be changed by heading to Blender add-on preferences (as above) and finding the item Guide Point Scale under Construction Line preferences. Once a scale is set here, all future guide points will be constructed at this new scale. To update existing guide points, start Construction Lines and select Scale All from the Context Menu


For a quick triangle, start drawing a circle and reduce the number of segments to three by pressing the keyboard down arrow.

You can change the current operation during use. For instance, whilst dragging out a rectangle shape, pressing L to change to the Line Tool, or C to change to the Circle Tool will retain the current start and end points but change to the new shape. You can also access the right-click context menu and chose an action, with the same effect. This is useful as the current start and end positions won't be reset.

If you require any support or have any suggestions for this add-on please use the contact page

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