Simple inset box - 2d Constraint

Joe Dunfee

Since I am fairly new to BricsCAD's implementation of 2D constraints, I realize I may not be going about this correctly.  Perhaps someone here can suggest an alternative approach. I want to create a simple rectangle, which has a smaller rectangle offset to the inside.  This is to represent a room, with a consistent wall thickness. Attached is the drawing, created as described below.

1) Starting with a blank drawing, and using the Imperial-Default template, I draw the outer rectangle.
2) Using the Offset command, I create the inner rectangle.
3) Using the 2D constraints, I fix the lower left corner of the outer rectangle.
4) Using the 2D Horizontal Dimension constraint, I dimension the lower left corners of the two rectangles.
5) Using the 2d Vertical Dimension constraint, I attempt to dimension the same two corners, but receive
    the following error message, "Could not create dimensional constraint."

In my past experience with programs like SolidWorks, this is something I would expect to work. Should this work in BricsCAD?  Is there an alternative method?

Thanks for the help,
Joe Dunfee

Scott McKenzie

 Hi Joe:

I just followed through the steps that you had outlined and have received the same result and I am not too sure why either.  

I did a bit of playing around and I did manage to get it to work:

1: Create your outer rectangle and then offset it inward to create the inner rectangle

2: Fix the bottom left corner of the outer rectangle

3: Add a vertical and horizontal constraint to the bottom and left side lines of the outer rectangle

4: Add a vertical and horizontal constraint to the bottom and left sides of the inner rectangle 

5: Add your horizontal and vertical dimensions between the rectangles

Interestingly, the following does not work, it also crashes when adding the dimensions:

1: Create your outer rectangle and then offset it inward to create the inner rectangle

2: Fix the bottom left corner of the outer rectangle

3: Create a parallel constraint between the bottom lines of the rectangles and the left lines of the rectangle

4: Add your horizontal and vertical dimensions between the rectangles

An option that would be very handy is to add constraints on the fly, for example, if you create a rectangle you should be able to tell the application to autoconstrain the rectangle by adding the appropriate angular, coincident, dimensions and parallel constraints so that it will remain a rectangle when you start adding additional constraints to other objects.

Joe Dunfee

Scott Said;
   I did a bit of playing around and I did manage to get it to work:

[Note that I broke down your steps, into even finer steps so that I can refer to it in the discussion.-joe]

    1: [a] Create your outer rectangle
        [b] and then offset it inward to create the inner rectangle

    2: Fix the bottom left corner of the outer rectangle

    3: [a] Add a vertical and horizontal constraint to the bottom
        [b] and left side lines of the outer rectangle

    4: [a] Add a vertical
        [b] and horizontal constraint to the bottom and left sides of the inner rectangle 

    5: [a] Add your horizontal
        [b] and vertical dimensions between the rectangles
----

Thank you for the effort, but I just followed the above sequence starting from a blank drawing, but get the same error message as before.  So, there does seem to be some variability in how it behaves. 

I will mention another issue I came across; I first attempted to apply the vertical constraints one after another, rather than the precise sequence you listed above.  But, I had second thoughts, and decided to delete the vertical constraint of the left inner rectangle line, so that it would match your sequence.  But, when I went to re-apply the vertical constraint to the same line after I had applied the horizontal.  My sequence was, 3a, 4a, delete 4a, 3b, 4a - but could not re-create 4a.

-Joe Dunfee

David Waight

Gentlemen,

I have also tried this and can confirm I get the same issue.

With a bit of experimentation I suspect it has something to do with the polylines that the rectangles are created from.

If you create the same scenario using individual lines and then create Coincident constraints using auto constrain and then add the geometric vertical/horizontal constraints and then the two dimensional constraints everything works as it should.

If you then try to turn the lines into polylines the dimensions immediately disappear.

I have never used Solidworks but could it be that it automatically creates coincident constraints as you draw entities similar to Autocad's inferred constriants?

Just a guess.

David Waight

Joe Dunfee

I recreated my example, but first exploded the polylines created by the rectangle command.  This time it worked.

I think this is a bug, since the manual says,
   "Horizontal and vertical geometric constraints force two points, a line or a polyline segment to
    be parallel to the X-axis (horizontal) or the Y-axis (vertical) of the current coordinate system. "

Note that since the plines are exploded, I had to constrain all 8 of the corners to have coincident points.  But, I can make the collection of this parametric object into a block.  Then, after exploding it, I can change the values.

-Joe Dunfee