topic Re: Isometric Drafting Verticals in AutoCAD Forum

Isometric Drafting Verticals

Anonymous — Wed, 02 Dec 2020 10:37:47 GMT

I am trying to draft sectional isometric. So a section cut and behind the cut is shown in iso. I drafted the section first then I changed the projection using the viewcube and turned on isometric drafting to isoplane top and started drafting the iso from the section. However the vertical lines i had in my section are now shorter somehow, my section looks squished. Does anyone know what I'm doing wrong?

Apologies if this is a rookie mistake, I'm still in college and relatively new to CAD.

Re: Isometric Drafting Verticals

Patchy — Wed, 02 Dec 2020 14:08:39 GMT

Unless you draw 3d, isometric drawing is still flat when you use the viewcube.

Re: Isometric Drafting Verticals

pendean — Wed, 02 Dec 2020 14:15:58 GMT

Isometric drafting is 2D: all you are doing is drawing in AutoCAD what you would draw on paper; you get the same result when you look at that paper from the side or angle or back.

You want to draw in 3D using 3D objects if you want all those 3D tools like section cut.

HTH

Re: Isometric Drafting Verticals

dbroad — Wed, 02 Dec 2020 14:31:41 GMT

You're views don't really look like isometrics. Here's a trick you might use to have both 2d and 3d objects.

Draw the sections orthographically in another drawing in model space, full size.
Copyclip or copybase the sectional objects to the clipboard.
In the drawing that has the live section, change the ucs to be a vertical plan aligned with the leftmost sectioned wall.
Pasteclip the sectional objects.
Change the ucs to a vertical plane at the rightmost sectioned wall aligned with the radial direction.
Pasteclip the sectional objects and mirror them.

I'm not sure that mixing 2d and 3d objects is really the best approach though.

Re: Isometric Drafting Verticals

leeminardi — Wed, 02 Dec 2020 16:02:46 GMT

It sounds like you want to combine some geometry you created in 2D then reposition your view to an isometric orientation and then continue 2D construction to the existing geometry but on a different plane. As @dbroad suggest, not a great workflow.

Please not that there is a difference between an isometric drawings and an isometric projections. An isometric projection is about 82% as large as an isometric drawing due to the foreshortening of the 3D lines that are not parallel to the projection plane. After changing the view to an isometric view and setting the UCS to View, scale the geometry by 1.2247. You can then work with the isoplane features at full scale.

The scale factor is determined by the fact that principal lines of 3D geometry are at an angle of about 35.2644 degrees (cos(1/sqrt(2)) with the projection plane in an isometric. The inverse of cos(35.2644) = 1.2247.

Re: Isometric Drafting Verticals

Anonymous — Wed, 02 Dec 2020 17:01:37 GMT

this is really helpful, thank you

Re: Isometric Drafting Verticals

Anonymous — Wed, 02 Dec 2020 17:02:52 GMT

Thank you, it took me a while to get my head around it but I think I understand now. I'm still new to CAD so I'm still learning.

Re: Isometric Drafting Verticals

Anonymous — Wed, 02 Dec 2020 17:04:41 GMT

Thank you, this is incredibly helpful!