January 12, 2012

ACA: Model Views and Annotation Scale

I made an interesting discovery yesterday, that may explain why I have occasionally had issues with viewports where the viewport scale and the annotation scale for the viewport are different. I suppose most people are a little more laid back than I am, and tend to draw on the Model "tab" without a lot of regard for how things will end up on the final sheet, and then compose the sheet on a Layout "tab" by eyeballing the corner points of the viewport, pan model space to get the target area roughly centered, use the scale control to set the viewport scale and then pan and/or adjust the viewport extents to suit. I like to think about how what I am drawing will eventually appear on a sheet, and work out how much of a sheet will be required for the drawing at hand. This often results in a non-plotting polyline in model space defining the extents of a particular drawing or detail, and I generally create a Model View of those extents, so that I can later create a viewport of the corresponding dimensions and restore that Model View and be done.

Yesterday's discovery was that I finally noticed that Model Views retain the annotation scale that is current at the time the Model View is created (when using the VIEW command). I did this while using ACA 2010; it may also occur in 2008 and/or 2009.
In the image above, you can see a Model View that I created of the area bounded by the yellow rectangle. This area is intended to be shown at 1/2" = 1'-0" (1:24) on a sheet. I "forgot" to change the annotation scale from the initial default of 1/8" = 1'-0", however, and so the Annotation Scale property of the Model View is 1/8" = 1'-0".

After drawing an appropriately sized viewport on a Layout tab and using the VIEW command to restore the Model View I created in that viewport, the viewport scale is correctly reported as 1/2" = 1'-0" on both the Viewport Scale control on the Drawing Window Status bar and on the Design tab of the Properties palette.
The Properties palette also reveals that the annotation scale associated with that viewport is the 1/8" = 1'-0" that was saved with the Model View. In most cases, having different viewport and annotation scales is not desirable. Note also that if you restore the Model View on the Model tab, the annotation scale will also be changed to that saved with the Model View. If the area is meant to be plotted at a particular scale, having that scale saved with the Model View would help automate getting the right scale associated with annotative content added as well as getting the the right scale when restoring the Model View in a viewport. So I am making a mental note to try to remember to set the annotation scale prior to creating a Model View. But can a Model View created with an incorrect annotation scale be fixed?

Unfortunately, the View Manager dialog does not provide a way to change the Annotation Scale property once the a Model View is created. You can rename the Model View, update the layer snapshot saved with the view (if any) and edit the boundaries of the Model View, but, as you may be able to tell from the gray background in the first image, the Annotation Scale property is not editable. I had hoped that while editing boundaries, that I would be able to change the annotation scale using the control on the Drawing Window Status bar, but that control is disabled when editing boundaries. In order to change the scale, you have to recreate/redefine the Model View, with the correct annotation scale set current prior to the redefinition. This is a fairly straightforward process, but it does require you to reselect the Model View boundaries.
  1. With the Model tab current, set the desired annotation scale.
  2. Start the VIEW command. In the View Manager, select the Model View to be recreated in the left pane, and then select the Name in the middle pane and copy the name to the clipboard. (You can skip this step if you are willing to type in the exact view name in the next step.)
  3. Click the New button. In the New View / Shot Properties dialog, paste (or type) the view name in the top edit box. Make any other changes to the settings in the dialog as desired.
  4. Click the Define view window button (or select the Define window radio button) and define the area of the Model View.
  5. Click OK in the New View / Shot Properties dialog. Choose Replace in the View - Already Exists dialog.
  6. In the View Manager dialog, note that the Annotation Scale property for the redefined Model View now matches the current, desired annotation scale.
  7. Click OK to dismiss the View Manager and register your changes.
  8. Return to the Layout tab and restore the redefined Model View in the viewport. Notice that now that the correct annotation scale is associated with the Model View, the viewport gets the correct annotation scale when the Model View is restored.

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