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real-unit edge lengths are not inclusive of object scale
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Description

System Information
Operating system: Windows 10
Graphics card: GTX 1080 Ti

Blender Version
Broken: 2.80 / 2019-04-23 23:28 / hash 0e78e3038d02
Worked: (optional)

Overlay measurement edge lengths don't adjust for object scale. As a result, they don't reflect the *actual* size of the object.

(but n-panel transform dimensions do)

Exact steps for others to reproduce the error

  1. In the scene panel, set the unit system to Imperial or Metric
  2. create a plane
  3. scale the plane bigger
  4. look at the dimensions of the plane in the N-panel
  5. TAB into edit mode
  6. open the Overlays menu, turn on Edge Length, select an edge
  7. Witness the length of the edge shown
  8. use the measure tool on the left to measure the edge... WITNESS they do not match!
  9. Apply transform
  10. witness they match

EXPECTED: real unit edge measurements to always represent real distances, regardless of whether object scale is applied or not

Event Timeline

William Reynish (billreynish) lowered the priority of this task from 90 to Low.Apr 4 2019, 12:41 PM

This has always been the case. Not sure if we should consider it a bug, but it does seem wrong/incorrect.

It follows the Global / Local setting from the Transform panel in the sidebar.

It's rather hidden, but also makes some sense for there to be one switch to control if you are viewing/editing global or local values.

William Reynish (billreynish) changed the task status from Unknown Status to Archived.Apr 4 2019, 12:47 PM

In that case it's not a bug.

The default value could perhaps be changed to Global?

Hmm, yes for measurement you most likely would want that, but not sure for regular vertex positions. In that case they would change and update for animated objects all the time.

On second thought, maybe that's ok too. There are lots of common cases where you'd prefer to have the absolute coordinates for vertices.

David Jeske (jeske) added a comment.EditedApr 4 2019, 8:20 PM

Here are some other ideas to consider: (not saying they are good)

(1) if you turn on measurements without the N-panel open, there is no visual indication anywhere of whether you're seeing local or global measurements

(2) would it be reasonable to show both measurements in the label when in local mode? For example... "2m (1.4m)" as in "global (local)"... this would prevent the user from mistaking a local unscaled measurement for a global one.

(3) would it be reasonable to only show local/untransformed measurements when Unit System is "None"? (i.e. when using real world Imperial or Metric units, always show "real" global transformed measurements)

(4) would it be reasonable to put an indicator in the label when it's a local coordinate? (such as the local icon)? .. As a caveat, if you are showing many measurements that's lots of repeated copies of that icon, since all measurements are in the same transform mode. Though, at least you would know it.

(5) perhaps consider duplicating the global/local transform setting right next to the overlay->measurement settings, since a user who is trying to use global measurements is unlikely to understand why they are displaying local or where to fix it.. but if the switch was right there when they turned them on, it would be more obvious.

(6) In general... what are the use cases around seeing local (untransformed) "real" unit measurements, like imperial and metric? What do other tools do? To me it seems a mistake to ever show a local/unscaled real world length unit, because a foot should be a foot should be a foot. Showing local (unscaled) measurements means you can put two equal size objects next to each other but edge lengths can show different real world measurements when in local mode and they have different transforms.

Simplest thing is just to set it to Global by default.

But, Local is useful for when an object is not in the world origin, but you still want to measure relative to the object origin.

Local is useful for when an object is not in the world origin, but you still want to measure relative to the object origin.

I can understand why you would want this for local vs world vertex coordinates..

However, edge-lengths and areas are never affected by translation offset to the world-origin. Are there cases where one wants to see object-local-scale measured edge-lengths and areas? Or is it possible these should always be global?

We also get many reports from users who would prefer if things like Bevel would be able to work with global coordinates too, which is also most often what you would want.

It could also be solved by making it so you can more easily scale objects without affecting the scale factor itself.

Most other 3d apps let you manipulate the basic dimensions of objects without applying a scale factor (because they all have some form of parametric modeling), which makes it much less likely to end up with odd-scaled items by mistake.

So these issues also tie into that.