Thursday, March 30, 2006

Who Wins? A Battle of Constraints

Using multiple constraints Revit can find itself caught in the middle. As a result some constraints will take precedence over others. Objects that are aligned will override length constraints.

If you apply both an alignment and length constraint Revit will complain that it cannot maintain both kinds of constraints. You can choose to remove the constraints. Revit will remove the length constraint and try to keep the alignment constraint.

This image portrays windows that are aligned and locked to each other and the first window has a locked dimension to position it near the wall.

Next we try to move the last window on the top right.

...and Revit complains...

Choosing Remove Constraints...the result...

Revit removes the length constraint and honors the alignment of the windows.

Similarly, equality constraints lose to length constraints. Do both of these on elements and Revit will offer the same warning. When you choose to remove constraints Revit will try to keep the length constraint and remove the equality constraint.

1 comment:

Patrick Johnson said...

The same rule to modeling should apply to Revit has it does to the manufacturing solid modeling.

First try and constrain with what is called a geometric constraint, if you can not use a geometric constraint then use the dimensional constrainted