Constraints on a simple rectangle

Joe Dunfee

 I am starting to investigate constraints.  I am hoping they will help me to create blocks that are easier to create for families of parts, since we don't have the ability to create dynamic blocks.

I added perpendicular constraints to 3 of the lines, and equal length constraint to opposite sides.  I didn't want to use horizontal or vertical, because I know I wanted to later be able to rotate the block in 90 deg increments.

As an investigation, I created a simple rectangle, and tried to edit by selecting it, and then grabbing one of the grips.  Some of the corners I can move and box will resize, but other corners will simply snap back. E.g. moving corner #1 left and right can resize it, but any vertical movement is ignored.  Corner #2 will  move vertically, but horizontal movement is ignored. No movement of corner #3 will do anything but snap back to its original size.

Is there a way to make a box that can be edited with grips and moving any one corner, with the box retaining its rectangular shape?

Note that I have also run into a number of bugs. E.g. when I copied my rectangle, the copy was the same as the original, but the original changed its size.  I repeated this several times, since it was so puzzling, and it did the same each time.  The vertical size got approximately double.  But, when I closed the drawing, and re-opened it, that bug went away.  Then, I noticed another bug. The copies had all their constraints showing, but the originals constraint icons disappeared   A regen would not bring them back. More copies of the original still could copy the constraints, so they were somehow still there, but not showing. Exiting BricsCAD and re-opening the drawing (which had been saved) did not bring the constraint icons back, though again copies of the rectangle will show them.

Are constraints a lost cause?

See the attached dwg for my example.  Again, note that the constraints are invisible.

-joe

Joe Dunfee

 I did find out how to show the disppearing constraint bars, using a tool on the constraint menu.  It also seems that constraints are hidden by default, when opening a drawing.  But, now I have a new question.

I can't find a way to hide dimensional constraints.  I suppose I can put them on a layer and have that layer off.  Is there any other way?

-Joe

Joe Dunfee

 It seems that once a dimensional constraint is created, its layer cannot be changed.

-Joe

Roy Klein Gebbinck

FWIW: I cannot reproduce any of the bugs you have reported in your first post.
What you are currently experimenting with is the way to go: you have to add more constraints to get predictable results.
Regarding your last question:
http://forum.bricsys.com/discussion/22919

Roy Klein Gebbinck

I forgot to mention that I have tested with V14.2.11.

Joe Dunfee

 I should also have mentioned my version.  It is 12.2.10.

Thank you for the link about changing the dimensional constraint layer.  Those methods work.  

Here is another one.  When I insert a block that features an object with dimensional constraints, and then refedit that block, all the dimensional constraints disappear. You cannot make any constraints appear.  So, using constraints in blocks is limited to the initial creation of the block, and if you edit the block as a separate drawing.  

I had hoped this would be a work-around for lack of dynamic block creation, and problems using existing dynamic blocks. I would just insert the parametric block I wanted, edit it, and then rename it to indicate its size, or what ever I changed.

At first I was thinking that my lack of familiarity with constraints was the issue, but now I am getting more convinced that there are a lot of problems with them.

-Joe

martin@enco.us

I don't think I'd recommend using V12 for evaluation of constraints.  The release notes for V13 and V14 have multiple entries for constraints.

Joe Dunfee

 Sorry, it was a typo.  I actually have 14.2.10.

On my rectangle example, I tried other approaches, such as setting opposite sides parallel and equal, and then two adjacent sized perpendicular.  But, still, I am limited by which corner I must grab to be able to resize. 

I finally had some success by not leaving a rectangle as a polyline, but rather, exploding it into lines and fully constraining it, including each end point.  Then by selecting any one element, I can use grips to control it.  If I were to select the whole rectangle, then it is still hit-and-miss, though it does behave better than the pline version.

I am experienced with constraints, from my work with SolidWorks, Inventor, ProEngineer. So, I have an idea what sort of behavior I should be expecting. Though, I should mention that in the past, constraints were quite problematic, being both difficult to predict and prone to crashing the program.  Though, in recent years all the programs have gotten much more predictable and reliable with constraints

-Joe