Hi All,
I have designed an extension to our house and have just sent this to a designer to create the bespoke panels.
He does not have SketchUp, so has asked for it to be exported as a .dwg file, which I have done. There now seems to be a discrepancy in the dimensions. Where I have drawn a wall at 120mm for example) he measures it at 126mm. My external walls of 250mm he measures as 263mm.
Cumulatively, this seems to be causing a problem. Any ideas?
Thanks,
Adam
Is he looking at the .dwg export as 2D? If so, make sure that you have set the Camera to Parallel Projection and chosen the appropriate standard view before export.
Thanks. I wonder if I could attach it here as a .dwg? Would you be able to open it and measure an external wall for example?
Why don’t you attach the .skp file so we can see what you are starting with for your export?
So we can’t see how you had it. Have you exported a new .dwg to send to the designer?
I do see that you have Length Snapping enabled in Model Info>Units. That should be turned off if you want to make your models with precision. I would also increase Display Precision so you can see small discrepancies if they occur.
Brilliant. Thanks. I have altered those settings too now, so I guess all I can do is export it again as a .dwg and see what he can see now.
Many thanks
This won’t magically change any inaccurate geometry.
Thanks for the comment. If you read the thread above, you will see that it’s not actually about inaccurate geometry, but thanks anyway.
I was commenting that turning off length snapping and re exporting will not correct any inaccuracies already in the file, should there be any.
But I haven’t seen the file or the export so ¯_(ツ)_/¯
Hi all,
I would like to confirm that I have the same problem.
For example Rectangle of the size 1000x1000 mm will export to dwg as 862x862 mm.
The projectction for the export is set to Orthographic so there is no perspective distortion.
Does anybody else experience this?
Thanks
Theo
Hello
Same than for the original poster, attach your skp file so other users can see what’s happening
Hi,
sure here are screenshots and files demonstrating the problem.
test.dwg (23.1 KB)
qube.skp (334.4 KB)
thanks,
Theo
yes.
in sketchup, you have a 3d cube. the cube is 1000mm wide. the line on screen isn’t 1000mm, it’s shorter due to your view. but SU knows it’s 1000mm.
in autocad you have a 2d projection of what’s on your screen. it’s not a cube anymore, it’s an hexagon. and because of the angle of the view in 3d, it’s now 816mm
if you want the same dimensions between SU and DWG you have to be in parallel AND face the element. if you’re in isometry, or any view that isn’t straight, then you’ll have shorted dimensions
Hi,
Thanks for the answer.
as you can see the exported geometry still represents cube just of the wrong dimensions.
Sorry I was bit inprecise, the view type in sketchup is set to Paralel not Orthographic.
Obviously the correct proportions are kept during the export as all sides of the cube are of the same dimension just not 1000mm.
And you are correct the dimensions in the standard front view are correctly exported to Autocad.
Why the iso view export is not treated the same as the standard front view?
thanks all,
Theo
Because it is not a real isometric view which is in fact a particular transformation of an axonometric view.
As pierre said, what you get is a projection of your cube on a 2d plan
Try it for yourself, draw a 100mm side square and project points at 45° from the corners on a perpendicular line, you’ll see it won’t be 100mm anymore
An isometric view is foreshortened. The dimensions are correct in the view plane. You would have to calculate the correct scale to scale the model up when exporting or to scale the drawing up afterwards in CAD.
Isometric drawing is actually a historic phenomenon, currently the only use is in some school drawing assignments.
Is there a way to get real orthographic - isometric view in sketchup or rather export to dwg?
Standard front view must be orthographic - paralel view as it provides correct dimensions.
Expected behavior of SketchUp is whenever the parallel projection is selected in the view panel the dwg export would be in correct dimensions as the one to one scale is selected.
Thanks Anssi,
I dont understand how parallel projection can be foreshortened. Are there any resources I should study to learn how it works?
Thanks
Theo
there is. you’ve already found it.
an isometry deforms the model so the 3 axis are now 120° appart. And often, to avoid visual deformation (the thing looks bigger than it actually is), a scaling is applied. A standard ratio is √(2/3) so about 0,816.
looking at the dimensions in your DWG, that’s the case with sketchup.
you could probably try scaling up by √(2/3) before hand to test.
Turns out another architect student (back then at least) had the same question, and she came up with an extension (@eneroth3 ) to make axonometric projections. It’s not just a way to place a camera, it will distort the model so it can be seen with an array of angles and scales.
handmade technical drawings.
When you learn to draw in 3d, it’s easy. you want to see something, just pivot.
when you learn to draw in 2d, especially by hand, you have to learn the tricks. the difference between perspective and all the axonometries out there
so if you want to know more,get your hands on an old technical drawings manual
