Topic: Understanding the differences between layer off and freeze

[daron]

This is a simple tutorial to help Autocad users better understand the differences listed.

* Note, for this experiment, you might replace my noting of layer 0 for a test layer of your naming.
It's my understanding that many cad users don't know or think there are differences between layers off and frozen states. I would like to demonstrate a couple things and allow the user to make his/her own determination of the differences. To start with, open a drawing with data in it. To make clear my first point, on layer 0 draw a series of objects (lines, points, etc.) around a fairly wide perimeter, so as to have the original data smaller than the extents of your viewing area. Now, turn off the 0 layer. Type zoom then extents. You should see very little in the way of movement. At least your original objects should still not take up the extents as you might expect. Now, turn layer 0 back on and then freeze it. Again, type zoom then extents. The original drawing should take up the extents of the drawing area.

Next example. Same drawing and objects on layer 0. Open your layer dialog box and freeze every layer, except 0. Thaw 0 if it is frozen, but turn it off. Exit the layer dialog. Now, type move enter all enter, then pick two points of a fairly wide distance. Reset your previous layer state and make sure layer 0 is on and thawed. You should see that all objects not on layer 0 are in place and all objects on layer 0 are moved.

From these demonstrations I hope anyone who didn't know the difference has come to a better understanding of the differences.

[mjfarrell]

Excellent Post Daron,

If I may let me add the following listing from the help file:

Visibility

Changes the visibility state of all the layers in the selected filter (or All or All Used Layers, if selected).

On: Objects on the layer are displayed, plotted, and regenerated and hide other objects when you use HIDE.  

Off: Objects on the layer are not displayed and not plotted but do hide other objects when you use HIDE. The drawing is not regenerated when you turn the layer on. Objects on Layers that are OFF are not shown, however they are considered to be present when CAD regenerates

Thawed: Objects on the layer are displayed and plotted and hide other objects when you use HIDE.

Frozen: Objects on the layer are not displayed and not plotted but do hide other objects when you use HIDE. The drawing is regenerated when you thaw the layer. Objects on Layers that are OFF are not shown, however they are considered to NOT be present when CAD regenerates


Lock

Controls whether the objects on the layers in the selected filter can be modified.

Lock: None of the objects on the layer can be modified. You can still apply object snaps to objects on a locked layer and perform other operations that do not modify those objects.

Unlock: Objects on the layer can be modified.
Viewport

In the current layout viewport, controls the VP Freeze setting of the layers in the selected layer filter. This option is not available for model space viewports.

Freeze: Sets Current VP Freeze for layers in the filter. In the current viewport, objects on the layer are not displayed and not plotted but do hide other objects when you use HIDE. The drawing is regenerated when you thaw the layer.

Thaw: Clears Current VP Freeze for layers in the filter. In the current viewport, objects on the layer are displayed and plotted and hide other objects when you use HIDE. This option does not thaw layers that are set to Off or Frozen in the drawing.

An easier manner to test this:  Draw a BOX on a Layer named BOX
Draw Line segment near the center of the box on a layer named Line.
Zoom Extents, Turn OFF the Box layer, and Perform another Zoom Extents, watch the result.

Now turn the BOX Layer On and then Freeze it, perform another Zoom Extents, and Observe.

In a production environment, this suggest use of various Layer State that have the Majority of your data layers FROZEN so as to improve your system performance while working in the drawing, and then other layer states, that one applies within various Viewports prior to publishing.

Additionally, IF and object is on a FROZEN Layer, and performs an operation, e.g. Move, or Erase, the objects are not affected. However IF the objects layer is simply OFF, the object will be moved, or erased, and you wont know it, because they are turned OFF.

[ronjonp]

If you plot to extents (like we do), it is very important that layers are frozen and not just turned off.

An addition of this to startup fixed any inconsistencies we were having

Code: [Select]

(defun rjp-layerschtuff (/ x)
  (vlax-map-collection
    (vla-get-layers
      (vla-get-activedocument (vlax-get-acad-object))
    )
    '(lambda (x)
       (if (= (vla-get-layeron x) :vlax-false)
(vl-catch-all-error-p
   (vl-catch-all-apply 'vla-put-freeze (list x :vlax-true))
)
       )
     )
  )
  (princ)
)
Ron