Dimensioning Confusion

Hello…new to this forum and to Rhino.
Running RH6 on a PC.

Anyhow, when I dimension a 3D object in perspective mode on the actual model, the value is correct.
However, when I do the same dimension on the layout, the number is completely incorrect.
For some reason, it appears that the dimensioning function is measuring the ACTUAL dimension of the object as it appears in the layout, versus the actual dimension of the modeled object? E.G., if you dimension a line in the layout, the number is a wrong number, but then you zoom out and redo the dimension and it shows that exact same line as being smaller?

There must be a simple answer to this, but I am also super confused as to why you would ever want your dimension on a layout to NOT reflect what you have modeled in full scale?

Hi Adrian - are you snapping the dimensions through to points on the 3d object in model space?
As far as I can see it is the same as previously - (V5)… it gives neither the paper dimension nor the 3d one, and I do not, right now, see what might be useful about this…

@adrian2 - so, I’m told, by people more familiar with dimensioning in general, that the possible utility of this bogus dimension would be to be able to modify it in Properties and put a custom note or value in there…


Well yes I did snap the dimensions in model space and the values were correct. But, when I did the exact same function in the layout, a different number appears. This of course both being on the perspective view.

Incidentally, this is NOT happening when I do the same actions in Front, Side or Top view?

Thank you…I received that same information via an email chat with Rhino tech support. It turns out that I wasn’t confused after all…ANY dimension on a perspective view will not be correct and apparently they said that function will NEVER be supported. I am fine with that, however it seems incredibly bad that you can actually have Rhino give an incorrect dimension versus not being able to do a dimension in perspective at all. I can only imagine somebody not being aware of this and sending a drawing to the floor for production.

As an old-time ink slinging drafter, the rule was dimensions should Never be shown unless they could be checked with a scale.
That means that dimensions were never shown in oblique or perspective views where they can not be checked.

Early on, for this reason, Rhino did not display dimensions in perspective viewports at all. Against my strong objections, we relaxed that old drafting “rule” for the sake of convenience.

Perhaps using the CurveLength “Text field” tool to create a piece of text or a Leader with the real length would work for you.