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Manual / Modify

Geometric Constraints (Parametric)

Add geometric constraints (horizontal, vertical, parallel, perpendicular, tangent and more) to a parametric 2D drawing.

What it does

A constraint forces a geometric relationship between objects. When you edit the drawing, the solver keeps that relationship. The result reports the remaining DOF (degrees of freedom), or fully constrained.

Where to find it

  • Ribbon: Parametric › Geometric and Parametric › Manage

Parametric tab
Parametric tab

Commands

Command Alias Button Meaning
GCHORIZONTAL GCH Horizontal The selected line is horizontal.
GCVERTICAL GCV Vertical The selected line is vertical.
GCPARALLEL GCPA Parallel Two lines are parallel.
GCPERPENDICULAR GCPE Perpendicular Two lines are perpendicular.
GCCOLLINEAR GCCOL Collinear Two lines lie on the same line.
GCEQUAL GCE Equal Equal length (lines) or equal radius (circles).
GCCOINCIDENT GCC Coincident The start points of two objects coincide.
GCCONCENTRIC GCCO Concentric Two circles share the same centre.
GCTANGENT GCT Tangent Two objects are tangent.
GCSMOOTH GCSM Smooth A smooth continuation between line and circle, or circle and circle.
GCSYMMETRIC GCSYM Symmetric Two objects are symmetric about the selected axis line.
GCFIX GCF, FIXCONSTRAINT Fix Fixes a line or circle in place.
GEOMCONSTRAINT GEOMCON – GEOMCONSTRAINT <type> applies any of the types above.
AUTOCONSTRAIN AUTOC Auto Constrain Automatically applies the constraints that are already true.
CONSTRAINTBAR CBAR Show/Hide Lists all constraints with their numbers (#0, #1, ...).
DELCONSTRAINT DELC Delete DELCONSTRAINT [n|all] deletes number n, all of them, or the latest one.
CONSTRAINTSETTINGS CSETTINGS Auto Constrain ▾ › Inference ON/OFF CONSTRAINTSETTINGS INFER ON|OFF

Steps

  1. Select the objects (1 or 2, depending on the constraint type).
  2. Click the button on the Parametric tab, or type the command, for example GCH.
  3. The result reads, for example, HORIZONTAL: 1 constraint(s) satisfied; 15 DOF remaining.
  4. If a constraint conflicts with an existing one, the program does not keep it (constraint not kept).

Constraint list after applying Horizontal, Vertical and Parallel
Constraint list after applying Horizontal, Vertical and Parallel

Try it: Big wooden coat button

A 40 mm plywood button for a chunky knitted coat. Draw it sloppily on purpose, then let the constraints line everything up.

  1. Rim: C, 0,0, 20, Esc. Engraved ring, slightly off-centre: C, 1,0.5, 16, Esc.
  2. Four holes in slightly different sizes: C -5,5 2, C 5,5 2.6, C -5,-5 1.8, C 5,-5 2.3. Press Esc after each one.
  3. Click the rim and type GCF. The rim is fixed in place.
  4. Click the rim, Ctrl+click the ring (click on the circle line, away from the blue grips), and type GCCONCENTRIC. The ring jumps to the centre.
  5. Click the top-left hole, Ctrl+click the top-right hole, and type GCE. Repeat for the top-left hole with the bottom-left hole, and the top-left hole with the bottom-right hole. All four holes now have the same size.
  6. Type CBAR. The list shows 5 constraints: fixed, concentric and three equal.

Coat button with a centred ring and four equal holes
Coat button with a centred ring and four equal holes

Challenge: Click any hole and type DCRADIUS 2. All four holes follow, because they are constrained equal.

See also