Revit perspective line weights

As promised, here is an obscure Revit tip - regarding line weights in perspectives. 

Have you ever been mystified by why the line weights might be nice and thin in a perspective view one day, but very heavy the next?  After some research, here is what I found (mostly on AUGI) and also what I figured out:

The actual line weight numbers for all 3D views including perspectives use the projection lineweight numbers set in Object Styles, which is the same setting used for projection lines in plans elevations etc.  This is not very subtle control, as you often want thinner lines in 3D views - so you need to use several methods to overcome this:

1. The "Thin Lines" tool only affects how the lines look on screen, not how they print or export to an image, so that is not much use.
2. You can use View Visibility to override the lineweight number in a given perspective view.
3. The actual display (and printing) of perspective lineweights is partly controlled by the Line Weights Settings (Manage, Additional settings), Perspective Line Weights tab. By default these are set to ridiculously large values - unless your template has been fixed.
       
4. Most people want thin lines on perspective views, so it is sensible to set the Perspective Line weights as small as possible (0.025mm in metric) - but they still end up looking a lot thicker than that.  You could make them all the same thinnest weight
   

    

   Metric perspective lineweights - default(left) and thin weights (right)

       

However, it isn't so simple - there are other things affecting the line weight

• The further your eye point is from the target point, the thicker the lines will appear.
• If you change the Perspective Line weights in your active file, it does not affect the line weights in linked files - you need to change the settings in each linked file to match.

So, even after doing the right thing with line weights you may still need to use a couple of tricks to get thin line weights when your eye point is at a great distance away:

1.  By default, when you create a perspective view, Revit makes the crop boundary quite small, so that when you place it on a sheet it might be only 150mm wide (6 inches). Increase the size of the crop on your perspective view, and this makes the lines look thinner, without affecting the view itself.  Don't forget to set it to "Scale (locked proportions)" before changing it.  
   First select the view boundary, then

   

   Default crop size

   
   

   

   Enlarged crop size

   
    [Thanks to "Patricks" in an AUGI thread for that trick].
   
2. If you want quick results (especially for linked files when you don't have time to change the line weights in them), use Visibility Graphics to override elements, categories or linked files and make them Halftone.  Or right-click and override by Element.
   
   
   When you print, just select the option to "Replace halftone with thin lines".  Revit will do just exactly that
   
   
   I haven't worked out how to apply this for exporting images, but you could print to PDF then convert to an image in Photoshop.

I hope this is useful to someone out there - it has certainly made a difference to our perspective print & export image quality.  Now, if only there was a "sketchy" or "freehand" lines checkbox in there too . . . . .