Installing and Using Construction Lines For Blender
Note: This add-on requires Blender 2.8 or higher (blender.org). This tutorial was made using Blender 2.83 so some screenshots and menus may differ slightly if you use a different version
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.
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.
Installing Construction Lines
Once you've downloaded the ConstructionLines.zip file, open Blender
Navigate to Edit->Preferences which will open a Preferences dialog
Click Add-ons in the left-hand buttons. Click the Install… button and find the downloaded .zip file.
Press Install Add-on from File. This will install the add-on.
To activate it click the checkbox where you see the 3D View: Construction Lines item (see below image).
You can now exit the Preferences Dialog.
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.
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
Hide/Show All - Hide and show all Guides
Scale All - Scale guide points based on the current zoom level
Remove All - Remove all Guides
Exit - Exit Construction Lines
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 prefered system under the Unit System and select units under Length.
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 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.
Guide points can be set by making a second clicked. This will create a new guide point and a construction line (guideline). Both guides are now snappable, so they can be used for snapping new measurements, geometry addition, or moving objects to a precise location.
Clicking once, typing in a distance and pressing Enter 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. The below image shows the colour change to blue when the axis lock is set to Z-axis.
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.
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.
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.)
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.
The number of segments for an arc or circle can be adjusted by using the up and down arrows on the keyboard whilst drawing. 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 divide faces with new shape geometry and add shapes to existing geometry, thus extending them.
NB. splitting a face is not always possible as Blender sometimes requires extra geometry to make this work. For instance, placing a new shape, unconnected to an existing face edge, will not divide the space. A feature to automatically add any extra geometry required to correctly split a face is currently in development for Construction Lines.
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.
"/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, then type "/2" and hit enter. 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.
Guide Point Half Way Along Measured Length
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.
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
Tip: Holding down alt whilst moving or dragging will temporarily disable snapping
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
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 now will 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)
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.
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