What is the parametric feature in AutoCAD?
Parametric drawing is a technology used for designing with constraints, associations, and restrictions applied to 2D geometry. There are two general types of constraints:
- Geometric constraints control the relationships of objects to each other
- Dimensional constraints control the distance, length, angle, and radius values of objects
Designing with Constraints
When you work with constraints, a drawing will be in one of three states:
Unconstrained. No constraints are applied to any geometry.
Underconstrained. Some constraints are applied to the geometry.
Fully constrained. All relevant geometric and dimensional constraints are applied to the geometry. A fully constrained set of objects also needs to include at least one Fixed constraint to lock the location of the geometry.
Thus, there are two general methods for designing with constraints:
You can work in an underconstrained drawing and make changes as you go, using a combination of editing commands, grips, and adding or changing constraints.
You can create and fully constrain a drawing first, and then control the design exclusively by relaxing and replacing geometric constraints, and changing the values in dimensional constraints.
The method that you choose depends on your design practices and the requirements of your discipline.
Use Constraints with Blocks and Xrefs
You can apply constraints between
An object in the drawing and an object within a block reference
An object within a block reference and an object within a different block reference (not between objects within the same block reference)
The insertion point of an xref and an object or a block, but not to any objects within xrefs
When you apply constraints to block references, the objects contained within the block are automatically available for selection. You do not need to press Ctrl for subobject selection. Adding constraints to a block reference can cause it to move or rotate as a result.
Constraints can be used in block definitions, resulting in dynamic blocks. You can control the size and shape of dynamic blocks directly from within the drawing. For more information, see Add Constraints to Dynamic Blocks.
Remove or Relax Constraints
There are two ways to cancel the effects of constraints when you need to make design changes:
Delete the constraints individually and later apply new constraints. While the cursor hovers over a geometric constraint icon, you can use the Delete key or the shortcut menu to delete the constraint.
Relax the constraints temporarily on selected objects to make the changes. With a grip selected or when you specify options during an editing command, tap the Shift key to alternate between relaxing constraints and maintaining constraints.
Relaxed constraints are not maintained during editing. Constraints are restored automatically if possible when the editing process is complete. Constraints that are no longer valid are removed.