Aligned Dimensions Bug?

Hi @lowell

Values of dimensions added in model space differ from values of dimensions added in paper space, while both dimensions snap to the same corner points of a box. Please see the steps below to reproduce and also the attached file.

  • New file
  • _Box at origin
  • _Layout
  • Double click in layout to activate viewport model space
  • Rotate top view into orthogonal projection with Ctrl-Shift RMB
  • _CPlane _3Point to a vertical face of the box
  • _DimAligned of corners of vertical face
  • Double click in layout to to switch back to paper space
  • _DimAligned of corners of vertical face
    –>> Reported dimension values differ, the dimension line drawn in model space shows the correct dimension.

Untitled.3dm (42.6 KB)

Hi Sillvano -
I see that in your example.
The PaperSpace dimension is in a different plane than the ModelSpace dimension and when it’s projected to the PaperSpace plane, the edge of the box is foreshortened and the value dimensioned is the length projected to PaperSpace.
For an easier to see example, rotate your box more as in the attached picture.
Dimension example

Hi @lowell

Thanks for your answer. I was aware of the different planes, but still expected the dimension to report the “actual” distance between the points. Thanks for the clarification.

I come from an “old school” of manual drafting where dimensioning of perspective views was NEVER allowed.
The general rule was dimensions should only be applied where they can be manually verified by checking them with a scale.

This is a perfect example of the dangers of dimensioning in a perspective projection.

Lowell touched on the key for Rhino; Rhino dimensions are always created coplanar to the current construction plane.

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