Not sure what the problem is but when dimensioning in an isometric view, the dimensions that are displayed are not what is actually in model space. Dimensions work just fine in top & side views regardless of viewport scale. I don’t understand why this doesn’t work in isometric views.
I want to bump this thread and ask whether there is any way to achieve this. I assumed using ‘Dim’ ‘Object’ might achieve this but it doesn’t. Requires endless work arounds to create what should be simple assembly drawings. Would love for a solution to this as well.
That depends on whom you talk to.
Dimensions are created coplanar to the Construction plane in the viewport you’re in.
That should be the hint you’re missing.
Old time Ink Slingers like me would say to Never show a dimension in a view projection that you can not drop a scale on and check it.
An isometric or perspective view is fine to include on a print, but I would have been fired for adding a dimension to one of those views.
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Hi @John_Brock
I would like to add my vote to fix this problem with isometric dimensions. I’ve had to dimension some isometric drawings and it is really a nightmare, almost impossible to achieve.
I start dimensioning in perspective view using the correct CPlane. Once I’ve finished, I change my view to isometric, select my model and dimensions and then I run _Make2D. The problem is that the measurements are changed after the projection. All the measurements have applied the same factor, around 80%. I guess this comes from some kind of trick used to show the actual model in isometric view.
One solution could be exploding dimensions previously to Make2D, but as you know Make2D doesn’t support text, so that’s not an option.
Could it be possible that after running Make2D all dimensions could get multiplied by the inverse factor so the dimensions could remain the same?
If you scale the Make2D results - including the dimensions - back up to the 1:1 scale, does that fix it? Normally scaling dimensions updates them to the new (scaled) value.
Yes, your solution works, thanks!! Technically this is not correct, but nobody is gonna measure it, so who cares ; ) Still, it would be nice to solve this issue so people don’t have to come here to find workarounds. Thanks again,
José
I agree it would be nice to have make2D output true 1:1 dimensions with all parallel projection viewports. I think this has been requested many times before, but I am not sure if it got on the bugtrack list - I didn’t find it immediately. @John_Brock
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From the developer:
I don’t understand this discussion.
Are all of the dimensions and geometry in ModelSpace?
If someone can make a file with one box and one dimension that doesn’t show the value it should, I’d be happy to look at why it doesn’t.
Hi @John_Brock
This image shows a 3D Cube in Isometric View with its corresponding dimensions.
This next one is the make2D result of that Cube. As you can see the dimensions don’t maintain the original value. Instead they have been multiplied by the same factor, around 80%. I guess this comes from some kind of trick used to show the actual model in isometric view. What we need is that those dimensions retain their original value.
isometricDimension.3dm (3.6 MB)
I hope this illustrate the issue clearly.
Cheers,
José
If you are in an Isometric projection, the dimension will be correct.
If you have run the Make2D command on that 3d box, then the curves will be not be their original length.
Rhino is displaying the actual curve length.
But why?
What actual curve length? Not the original curves (edges) in any case. And the scale it does display - 0.8165 - (relative to the original) looks to be arbitrary…
Because they have been flattened by Make2D.
This is the reason that Dimensions that are not parallel to the view should never be shown, as they are foreshortened by the projection, and can not be checked with a scale on a print.
OK, I will concede that point, sorry for the argument… 
Here’s how to prove you are correct and to see that the scale is not arbitrary.
- Make a cube in some standard size
- Set the Perspective viewport to Isometric view via the isometric command (say SE).
- ExtractWireframe on the cube and delete the original
- Set CPlane>ToView in the Parallel (Isometric) viewport
- Select the wireframe and use ProjectToCPlane - delete originals
- Use RemapCPlane to remap the projected wireframe from the current CPlane to Top.
- Measure the results. The cube edges will be 0.8165 times the original lengths
I disagree here. The whole point of having dimensions in a isometric view is exactly that, to not have to use a scale ruler on a print!