From: saltab
Hi,
I often use the MAKE2D OR MAKE2D4VIEWS command to generate technical drawings for presentations.
When I make a 2D drawing from a Top, Front or Left view, the result is a 1:1 scale drawing projected on the TOP view, which is great. However, when I make a 2D from a 3D view set as isometric (REF:
https://moi3d.com/forum/index.php?webtag=MOI&msg=1917.35) the result is always a drawing that is 81.63% smaller than the correct dimension. So I have to apply a scale factor of approx. 1.225 to get the correct size.
To be honest, this is not a major issue as I can easily scale the drawing, however I wonder if there is a reason why I get this specific result.
From: Michael Gibson
Hi saltab, for all parallel projections the result from Make2D will preserve scale for lines that are parallel to the view plane.
For the case of an isometric view, the preserved scale will be for lines like this:
If you run Make2D on that isometric view, you should get a result with the 2D projection of that line being the same length as the 3D line, like this:
The other lines will not have the same length as their 3D source lines, because those lines do not have both ends on a plane parallel to the view plane.
That's just the same behavior as Top/Front/Right views, lines that are not parallel to their respective view planes will also not maintain the same length when projected either.
Does that help explain what you're seeing ?
I guess another way to describe it would be that it is preserving scale but it's in a different direction than what you were thinking?
- Michael
Image Attachments:
make2d_isometric_scale1.png
make2d_isometric_scale2.png
From: Michael Gibson
Hi saltab, so the upshot is that there is an "Isometric scale" (your 1.225 value) that you need to apply if you want to make isometric axis lengths preserved instead of view plane lengths preserved.
Some info here:
https://www.jntukmaterials.com/wp-content/uploads/2019/05/textbook-of-engineering-drawing_compressed-4-2.pdf
https://rskr.irimee.in/sites/default/files/Isometric%20Drawings.pdf
https://gppanchkula.ac.in/wp-content/uploads/2020/04/Axonometric-projection-.pdf
- Michael
From: saltab
Hi Michael!
I thought that number should have an explanation... I am glad to finally know where it comes from! :)
Many thanks!
Salvatore
