Construction Lines - Accurate Cad Modelling Add-On For Blender

by Dan Norris in Scripts and Addons

CAD Modelling for Blender

Overview And Key Functions

Construction Lines is a tool for accurate CAD style modelling. Build snappable guide points and edges, draw lines and primitive shapes in place, automatically create faces in closed geometry and precisely move object geometry around a scene.

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.

If you come from software packages such as SketchUp this is a perfect way to get started with Blender

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

Price Reduced in Beta

Guide Edges & Points

Drawing Lines


Drawing Shapes In Place


Precise Object Moving 



Feature List

  • Create snappable guide edges and points
  • Precisely measure distances
  • Build rectangles, circles and arcs anywhere in your scene
  • Draw lines simply by clicking and dragging in the 3D viewport
  • Lines will automatically fill in faces where geometry is closed
  • Use lines or shapes to cut into or divide existing geometry 
  • Build lines, shapes and guides to exact size with numeric input (including mathematical operators * / + -)
  • Limit drawing and movement to  the X, Y or Z axis
  • Auto snap to Perpendicular edge direction and edge extensions
  • Accurate object movement with snap points or numeric input
  • Create faces from a list of selected snap points (vertex, edge, edge center, face)


Features In Development

  • Automatic face splitting when adding a new shape away from an edge in existing geometry (Blender won't split a face if there is not a connecting edge)
  • Angle measurement between objects/geometry points
  • Rotation of guidelines/objects to a snapped point - means you can rotate and snap to a distant unconnected vertex/edge/face


Current Version

Version 0.9.3

Release Notes:

Features & Updates: 

  • Snapping can now occur when line/tape is dragged perpendicular or is an extension to an edge (snap is highlighted for both cases - pink for perpendicular and purple for edge extension)
  • Numeric input is now triggered after the Enter key is pressed. This allows for the Numpad and number row to be used for camera orientation during normal operation. Pressing Enter again, after typing a value, will apply the number/expression to the current operation
  • Select a guide edge and create true geometry for use outside of CL using the context menu (hold Shift and click guide edge to select. The guide will change to an orange colour when selected )
  • Added new preference to override Unit Length with Unit Scale when adding guides and new geometry (this is useful when working with custom scales)
  • Added new preference to set guide scale. This will affect all new guide points. Existing guides can be updated by using Scale All from the context menu
  • Default scale for guide points is now smaller
  • 3D mouse events are now passed through to Blender, so using a 3D mouse to navigate should now be possible
  • Strength of axis snapping has been reduced, allowing for greater freedom of movement when drawing and measuring


Bug Fixes:

  • Fixed OpenGL issue with dashed tape measure not displaying on some Apple Mac computers
  • Fixed bug when calling undo multiple times, where undo will lead outside of current Blender context and cause a crash
  • Fixed issue with correct measurement display when changing length units
  • Fixed bug which allowed some non-numeric values to be used in metric mode input, causing a crash
  • Fixed issue with numeric input when using Imperial units and typing a number with greater than one decimal place as the first value
  • Mouse clicks outside of viewport area are now handled correctly (either passed through to Blender or ignored)
  • RGB values for guide colour in preferences are now correctly limited
  • Numerous performance and stability improvements along with lots of minor fixes


Version 0.9.2

Release Notes:

  • Big performance improvements when cutting into existing geometry
  • Fixed stability issues when using shapes to cut into existing geometry


Version 0.9.1

Release Notes:

Minor update

Please note that upgrading from version 0.9.0 requires removal of version 0.9.0 from Blender before installing any new version. 

  • Dimension input now allows for Imperial values (when Blender's Unit System is set to Imperial) - Values can be written in multiple ways eg. 12'1" 3/8, 12'1, 12' 3/8, 12. Decimals can be used for the first value. Will work with either Feet or Inches set as the Length Unit
  • Hold Ctrl and using the mouse wheel will allow for changes in circle/arc segments and will also automatically add guide point divisions to the current guide edge - Whilst dragging a guide edge use Ctrl+Mouse Wheel to increase/decrease the number of guide divisions
  • A guide point is now added to the start of a guide edge
  • Bug fix to arc and circle when using with existing geometry face - was not cutting correctly - NB. This is a patch fix, the face finding and face intersection system will be re-written for the next Construction Lines Version
  • Bug fix to measurement scale - was not previously taking into account the user-entered Unit Scale only unit type scale 

Inital Version

Version 0.9.0 Initial Beta Release