I would love to see more robust line-weighting, particularly line weight preview, find its way into Rhino 6. I think Rhino 5 is a great starting point, and I would hope that any of my thoughts that seem worthwhile would be easy to implement.
I am an architect and bring that perspective to these comments. Additionally, all of my comments are focused towards 2D, parallel projection drawings, e.g. architectural drawings, the results on Make2D, etc.
The “Scale by” multiplier in Print Setup dialog
I use this all the time, and find it particularly useful to tune my standard layer line weights to a particular drawing or scale. It seems to be an application setting, rather than a document setting, which I find particularly frustrating: if someone else on my team opens a file and prints, it is likely that they will end up with a different print outcome. Similarly, I am often working on multiple projects through the course of a day or week, and currently I have to remember (or guess-and-check) the “Scale by” value for each project as I jump back and forth. I would encourage that this setting should be saved with each document. (Personally, I would like to be able to set this per layout, but this may create an added layer of complexity that’s not beneficial to a typical Rhino user).
I have also noticed that Print Preview/PreviewDisplay does not factor in the “Scale by” setting, which means the Print Preview isn’t necessarily a reflection of the print outcome. I believe Print Preview, whether on a layout, in a detail or in a standard viewport should acknowledge the “Scale by” factor, so that what is displayed on screen matches the print outcome as closely as possible.
Print Preview in Layout / No Detail Activated
This is the most useful line weight preview tool. With the exception of ignoring the “Scale by” factor, it generates a perfect preview of the print outcome.
Print Preview in Layout / Detail Activated
As soon as the detail is activated, the line weight preview stop working (even if Print Preview is checked in the detail). Is this a bug? It would be great if Print Preview worked inside the detail so that the line weights reflect the print outcome (which would mean zooming in results in the lines appearing wider, and zooming out results in the lines appearing narrower).
Print Preview in Standard Viewport
I find this to be the least useful line weight preview tool. It does a nice job of showing line weights relative to one another, but is completely abstract relative to actual print width. (For me, and I suspect for many others, zooming is a necessary part of designing/modeling, but level of zoom is always abstract relative to final output, be that a scaled drawing or a 1:1 fabrication). The PrintDisplay command has a Thickness option, and I completely understand this for Perspective viewports, which are without scale. But it would be great if Parallel viewports could have a Scale option instead that would display line weights as they would appear if printed at that scale (which would mean that, as above, zooming in results in the lines appearing wider and zooming out results in the lines appearing narrower).
I would be happy to elaborate further if that would be helpful.