﻿ Geometry | Coincident

# Geometry | Coincident

Command:

Click Add Coincident Constraint, then click:

 • two Lines (or: a Line and the X-axis or Y–axis)

- or -

 • a Point and a Line (or a Circle), (or a Point and the X-axis or Y–axis)

- or -

 • two Points

- or -

 • or a Point and a Motion-Point

To delete

 1 Click a sketch-element that is 'coincident' with a different sketch-element...

The sketch-element and the constraint show in the Selection-Window.

- or -

 1 In the Geometry Tree, explore the 'Constraint Loops' to find the Coincident constraint
 2 Click the Coincident constraint.

It now shows in the Selection-Window.

 2 Right-click the Coincident constraint in the Selection-Window
 3 Click 'Delete' in the contextual menu

Result:

If the two sketch-elements have more than two degrees-of-freedom:

 • the two Lines (or a Line and the X or Y–axis) become co-linear

- or -

 • the Point becomes coincident with the 'ray' of the Line, or with the circumference of the Circle

- or -

 • the two Points become coincident.

Note: If there is a total of 1 degree-of-freedom, then the two elements will not become 'coincident'.

In MechDesigner, you cannot, remove more than two degrees-of-freedom of a Point. For example, you cannot in do these two steps:

 STEP 1: Add a Coincident Constraint between a Point and a Line (or axis) - this removes 1 degree-of-freedom from the Point.
 STEP 2: Add a Coincident Constraint between the same Point and another Point - this attempts to remove a further 2 degrees-of-freedom - it CANNOT!

Why:

 • A Coincident Constraint between a Point and a Line removes 1 DOF from the Point.
 • A Coincident Constraint between a Point and a Point removes 2 DOF from the Point.

Thus, delete the constraint between the Point and the Line (STEP 1), before you add the constraint between the two Points (STEP 2).

 • '+' : centre-Points - at the centre of Arcs and Circles
 • 'O' : start-Point or end-Point - at the end of a Line and Arc
 • : centre-Point that is coincident with a start-Point or end-Point.

You may need to select the '+' or the 'O' with a command, and it is important to see the difference between the two Points and be able to select one Point or the other Point.

When a centre-Point is Merged with a start-Point or end-Point of a Line or Arc, the symbol is a '+'. You cannot select one or the other, because there is only one Point.

 • : Motion-Point - added to a sketch-element with Add Motion-Path FB.
 • : Motion-Point coincident with a start-Point or end-Point.

Compare with Merge-Points, Horizontal, Vertical

Notes:

Use Add Coincident between two Points for construction geometry.

Use Merge-Points for sketch-loops and sketch-paths.

Points that are 'coincident' give you the option to delete the Coincident Constraint later.

### Coincident constraints in the Graphic-Area, Selection-Window and Geometry-Tree.

Before

After

Select:

In Selection-Window &

Geometry-Tree as...

 • Two Lines:
 • Line and X or Y–axis

The Lines become co-linear

CoincidentLtoLn

 • Point and Line (or X & Y–axis)
 a. The Point lies on 'ray' of the Line.

CoincidentPtoLn

 b. A Point in a sketch-element and Line

 c. The X or Y–axis or Ray of the X or Y–axis.

 • Point and Circle:

The Point is constrained to lie on the circumference of a Circle

CoincidentPtoCn

 • Point and Point:

The Points become coincident

CoincidentPtoPn

Help Files for MechDesigner and MotionDesigner 11.1 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd