---------------
In a case where a sketch has 2 horizontal lines and a verticle at the
Mid-Point of each line, it will display the midpoint constraint symbol. Adding
a Collinear constraint will cause the 2 lines to be positioned on top of each
other. Now the MidPoint constraint no longer displays graphically or in the
Quick Pick menu. But it still shows in the Show/Remove Constraints menu. Why
doesn't it display?
Solution
After adding the collinear constraint, the verticle line that was between the
reference edge and horizontal line still exist, but is very small. In fact, it
is a zero length line, but it still exist. The symbol will not display with
small geometry.
There is a Sketch Preference setting called "Dynamic Sketch Display" if toggled
OFF, then the symbols will display. So, while in the sketch, go to Menu -->
Preferences --> Sketch --> Session Settings (tab) --> Dynamic Sketch Display.
Here is the documentation on the Dynamic Sketch Display;
Go to;
CAD --> Sketching --> Sketch Preferences: what do you want to do?
Dynamic Sketch Display
======================
When this option is selected, constraint and vertex symbols do not display if
the associated geometry is very small. To see these sketch objects regardless
of associated geometry size, clear this check box.
Notes and References
Hardware/Software Configuration
Platform: all
OS: n/a
OS Version: n/a
Product: NX
Application: DESIGN
Version: V10.0
Function: SKETCHER
Ref: 001-7713191