Isometric measurements wrong - "SOLVED"

I have seen this discussed dating a few years back.
When I do a parallel view and then in layout I set the scale to say 1:1 I would expect that a cube of 100 x 100 X 100 show the side of the cube to be 100 mm, instead it comes 81.649658 mm.
The only advantage (and don’t use it much) of an isometric is to be a 3D illustration, which is also measurable. If it is not it beats the purpose.
Any ideas?
PS. by the way I was just about issuing a series of contractual drawings with scaled isometric drawings.

Hi, it has been a week or two but Steve had some questions on the same issue. Maybe you have read it, if not you may find some answers there.

Hi Mark,
maybe I am missing something. I am not sure how to the topic you refer to.
I tried “Steve isometric” without success. I’m not even sure who is Steve… sorry, Steve.

This is really puzzling me since yesterday night and I am really wonder what to do with my submission.

Actually I just realized it is really bad. I have about three layouts with 20 details each at (supposedly) 1:10 iso views, that perfectly fit in the A0 page. Now I realized that if they would be actually 1:10 they would not fit, so there goes a whole lot of layouting work down the drain.

Any ideas on how to solve this for the future?

Why is my distance in an isometric off - might be helpful?

Thank you Norsemen23
I had come across that thread. It is about, i think, the make2d command. Here I am talking about the layout view. but indeed the ªdistortionª seems to be very similar. However @pascal suggested scale does not seem to work here.
It also was almost 3 years, I was hoping there had been some progress on this.
Thanks anyway.

The python script skews the model so it could potentially work for you in layouts (the dimensions are correct). You may need to edit it though to orient your models properly.


By skewing you mean it distorts and alter the model it self? In that case, I don’t think it will work, it is a relatively complex model and I would rather not distort the model.

In the layout actually, all you have to do is make the scale of the viewport 1: 0.816497 to make it 1:1, or 1 : 8.16497 for 1:10.

That the solution is so “simple” makes it a bit more frustrating that has not been fixed.
I am just curious now if there is a reason for this and why 1 : 0.816497?

IMO there is nothing to be fixed.

What Rhino does to turn 3D data into 2D is a simple projection.
That is projecting 3D points perpendicularly onto a plane.
Obviously if we project a line, the length of the projected line varies with the angle formed with the direction of projection.
If the line is parallel to the projection plane, its length does not change.
If it is normal to that plane, we only get a single point.

The length of the projected line is reduced by the sine of the angle between the line and the plane normal (the direction of projection)
In an isometric view, this angle is about 54.74 degrees ( You can check that by drawing a cube in Rhino and a diagonal line between two farthest vertices )

0.8165 … is exactly the sine of that angle.

An axonometric view is a different thing with its own rules.
Obviously we may ask for axonometric views in Rhino, But they are different from the parallel (or perspective) projection that Rhino has always used.

( Sorry if my words are not clear … poor English and pretty confused ideas too …:confused: )

Hi Emilio,
Thank you for taking the time to pointing me to the obvious… you are right…
I suffered from my old age… when I was young :sleeping: … we used to build up the isometric perspectives by using the scaled dimensions in the xyz axis so on the 30, 90 and 120 degrees directions, and I assumed that would be the 1:1 scale by convention for parallel projections… so when I chose the scale in the viewport, I expected a certain behaviour… Obviously, not all parallel projections are axonometric…
Thanks again.
PS - I added “SOLVED” to the tittle - not that something was solved… besides the knot in my mind…

Hi N

Well, I’d say not necessarily so obvious :slight_smile:
We all expect Rhino to do what we are used to do … ( I’ve been young many years ago too … :wink: )

Then in architecture people expect axonometry
Others expect better tools for moulds or foundry … etc.

We all try to steer Rhino where we need. And try hard to find ways in Rhino to do what we need but Rhino does nor care about … :smile:
I think, when you’re a Rhino user, that is the rule of the game. :smiley: